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Store the data in .csv file
file=open("toronto-data.csv","wb") file.write(bytes(tabela1,encoding="ascii",errors="ignore"))
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MIT
Exploring-the-neighborhoods-in-Toronto.ipynb
Gabriellavoura/Coursera_Capstone
Converting into dataframe and assigning column names
import pandas as pd df = pd.read_csv('toronto-data.csv',header=None) df.columns=["Postalcode","Borough","Neighbourhood"] df.head(10)
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MIT
Exploring-the-neighborhoods-in-Toronto.ipynb
Gabriellavoura/Coursera_Capstone
Drop row where borough is "Not assigned"
# Get names of indexes for which column Borough has value "Not assigned" indexNames = df[ df['Borough'] =='Not assigned'].index # Delete these row indexes from dataFrame df.drop(indexNames , inplace=True) df.head(10)
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MIT
Exploring-the-neighborhoods-in-Toronto.ipynb
Gabriellavoura/Coursera_Capstone
If a cell has a borough but a Not assigned neighborhood, then the neighborhood will be the same as the borough
df.loc[df['Neighbourhood'] =='Not assigned' , 'Neighbourhood'] = df['Borough'] df.head(10)
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MIT
Exploring-the-neighborhoods-in-Toronto.ipynb
Gabriellavoura/Coursera_Capstone
Rows will be same postalcode will combined into one row with the neighborhoods separated with a comma
result = df.groupby(['Postalcode','Borough'], sort=False).agg( ', '.join) df_new=result.reset_index() df_new.head(10)
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MIT
Exploring-the-neighborhoods-in-Toronto.ipynb
Gabriellavoura/Coursera_Capstone
Store data in new .csv with clean data.
df_new.to_csv(r'Toronto-data-processed.csv', index = False, header = True)
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MIT
Exploring-the-neighborhoods-in-Toronto.ipynb
Gabriellavoura/Coursera_Capstone
Daily Return Distribution (For 15 years)
daily_returns = (nifty_data['Close']/nifty_data['Close'].shift(1) - 1)*100 daily_returns = daily_returns.dropna() daily_returns.describe() plt.figure(figsize=[8,7]) plt.style.use("bmh") plt.hist(daily_returns, density = True, bins=20, color='#2ab0ff',alpha=0.55) plt.xlabel('% return', fontsize=15) plt.xticks(fontsize...
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Apache-2.0
notebooks/Daily and Weekly Returns.ipynb
yantraguru/niftystats
Weekly Return Distribution (For 15 years)
weekly_nifty_data = nifty_data.resample('W').agg(niftyutils.OHLC_CONVERSION_DICT) weekly_nifty_data.index = weekly_nifty_data.index - to_offset('6D') weekly_returns = (weekly_nifty_data['Close']/weekly_nifty_data['Close'].shift(1) - 1)*100 weekly_returns = weekly_returns.dropna().rename('returns') weekly_returns.descri...
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Apache-2.0
notebooks/Daily and Weekly Returns.ipynb
yantraguru/niftystats
Writing Reusable Code using Functions in Python![](https://i.imgur.com/TvNf5Jp.png) Part 4 of "Data Analysis with Python: Zero to Pandas" This tutorial covers the following topics:- Creating and using functions in Python- Local variables, return values, and optional arguments- Reusing functions and using Python librar...
today = "Saturday" print("Today is", today)
Today is Saturday
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
You can define a new function using the `def` keyword.
def say_hello(): print('Hello there!') print('How are you?')
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Note the round brackets or parentheses `()` and colon `:` after the function's name. Both are essential parts of the syntax. The function's *body* contains an indented block of statements. The statements inside a function's body are not executed when the function is defined. To execute the statements, we need to *call*...
say_hello()
Hello there! How are you?
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Function argumentsFunctions can accept zero or more values as *inputs* (also knows as *arguments* or *parameters*). Arguments help us write flexible functions that can perform the same operations on different values. Further, functions can return a result that can be stored in a variable or used in other expressions.H...
def say_hello(name): print('Hello {}'.format(name)) say_hello("John") say_hello("Jane") def filter_even(number_list): result_list = [] for number in number_list: if number % 2 == 0: result_list.append(number) return result_list
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Can you understand what the function does by looking at the code? If not, try executing each line of the function's body separately within a code cell with an actual list of numbers in place of `number_list`.
even_list = filter_even([1, 2, 3, 4, 5, 6, 7]) even_list filter_even([1, 3, 5, 7])
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Writing great functions in PythonAs a programmer, you will spend most of your time writing and using functions. Python offers many features to make your functions powerful and flexible. Let's explore some of these by solving a problem:> Radha is planning to buy a house that costs `$1,260,000`. She considering two opti...
def loan_emi(amount): emi = amount / 12 print('The EMI is ${}'.format(emi)) loan_emi(12_60_000)
The EMI is $105000.0
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Local variables and scopeLet's add a second argument to account for the duration of the loan in months.
def loan_emi(amount, duration): emi = amount / duration print('The EMI is ${}'.format(emi))
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Note that the variable `emi` defined inside the function is not accessible outside. The same is true for the parameters `amount` and `duration`. These are all *local variables* that lie within the *scope* of the function.> **Scope**: Scope refers to the region within the code where a particular variable is visible. Eve...
emi amount duration
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
because above variables are all the local variables We can now compare a 6-year loan vs. a 10-year loan (assuming no down payment or interest).
loan_emi(12_60_600, 8*12) loan_emi(12_60_000, 10*12)
The EMI is $10500.0
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Return valuesAs you might expect, the EMI for the 6-year loan is higher compared to the 10-year loan. Right now, we're printing out the result. It would be better to return it and store the results in variables for easier comparison. We can do this using the `return` statement
def loan_emi(amount, duration): emi = amount / duration return emi emi1 = loan_emi(12_60_000, 8*12) emi2 = loan_emi(12_60_000, 10*12) emi1 emi2 emi1 - emi2
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Optional argumentsNext, let's add another argument to account for the immediate down payment. We'll make this an *optional argument* with a default value of 0.
def loan_emi(amount, duration, down_payment=0): loan_amount = amount - down_payment emi = amount / duration return emi emi1 = loan_emi(12_60_000, 8*12, 3e5) emi1 emi2 = loan_emi(12_60_000, 10*12) emi2
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Next, let's add the interest calculation into the function. Here's the formula used to calculate the EMI for a loan:where:* `P` is the loan amount (principal)* `n` is the no. of months* `r` is the rate of interest per monthThe derivation of this formula is beyond the scope of this tutorial. See this video for an explan...
def loan_emi(amount, duration, rate, down_payment=0): loan_amount = amount - down_payment emi = loan_amount * rate * ((1 + rate)**duration) / (((1 + rate)**duration)-1) return emi
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Note that while defining the function, required arguments like `cost`, `duration` and `rate` must appear before optional arguments like `down_payment`.Let's calculate the EMI for Option 1
loan_emi(12_60_000, 8*12, 0.1/12, 3e5)
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
While calculating the EMI for Option 2, we need not include the `down_payment` argument.
loan_emi(12_60_000,10*12, 0.08/12)
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Named argumentsInvoking a function with many arguments can often get confusing and is prone to human errors. Python provides the option of invoking functions with *named* arguments for better clarity. You can also split function invocation into multiple lines.
emi1 = loan_emi( amount = 12_60_000, duration=8*12, rate=0.1/12, down_payment=3e5 ) emi1 emi2 = loan_emi(amount=1260000, duration=10*12, rate=0.08/12) emi2 def round_up(x): emi2 = loan_emi(amount=1260000, duration=10*12, rate=0.08/12) return round(emi2) round_up(emi2)
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Modules and library functionsWe can already see that the EMI for Option 1 is lower than the EMI for Option 2. However, it would be nice to round up the amount to full dollars, rather than showing digits after the decimal. To achieve this, we might want to write a function that can take a number and round it up to the ...
import math help(math.ceil) math.ceil(1.2)
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Let's now use the `math.ceil` function within the `home_loan_emi` function to round up the EMI amount. > Using functions to build other functions is a great way to reuse code and implement complex business logic while still keeping the code small, understandable, and manageable. Ideally, a function should do one thing ...
def loan_emi(amount, duration, rate, down_payment=0): loan_amount = amount - down_payment emi = loan_amount * rate * ((1+rate)**duration) / (((1+rate)**duration)-1) emi = math.ceil(emi) return emi emi1 = loan_emi( amount=1260000, duration=8*12, rate=0.1/12, down_payment=3e5 ) emi1 emi...
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Let's compare the EMIs and display a message for the option with the lower EMI.
if emi1 < emi2: print('Option 1 has the lower EMI: ${}'.format(emi1)) else: print('Option 2 has the lower EMI: ${}'.format(emi2))
Option 1 has the lower EMI: $14568
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Reusing and improving functions Now we know for sure that "Option 1" has the lower EMI among the two options. But what's even better is that we now have a handy function `loan_emi` that we can use to solve many other similar problems with just a few lines of code. Let's try it with a couple more questions. > **Q**: Sh...
cost_of_the_house = 800000 home_loan_duration = 6*12 #months home_loan_rate = 0.07/12 #monthly home_down_payment = .25 * 800000 emi_house = loan_emi(amount=cost_of_the_house, duration=home_loan_duration, rate=home_loan_rate, down_payment=home_down_payment)...
Shaun makes a total monthly payment of $96632 towards loan repayments.
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Exceptions and `try`-`except`> Q: If you borrow `$100,000` using a 10-year loan with an interest rate of 9% per annum, what is the total amount you end up paying as interest?One way to solve this problem is to compare the EMIs for two loans: one with the given rate of interest and another with a 0% rate of interest. T...
emi_with_interest = loan_emi(amount=100000, duration=10*12, rate=0.09/12) emi_with_interest emi_without_interest = loan_emi(amount=100000, duration=10*12, rate=0./12) emi_without_interest
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Something seems to have gone wrong! If you look at the error message above carefully, Python tells us precisely what is wrong. Python *throws* a `ZeroDivisionError` with a message indicating that we're trying to divide a number by zero. `ZeroDivisonError` is an *exception* that stops further execution of the program.> ...
try: print("Now computing the result..") result = 5 / 0 print("Computation was completed successfully") except ZeroDivisionError: print("Failed to compute result because you were trying to divide by zero") result = None print(result)
Now computing the result.. Failed to compute result because you were trying to divide by zero None
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
When an exception occurs inside a `try` block, the block's remaining statements are skipped. The `except` block is executed if the type of exception thrown matches that of the exception being handled. After executing the `except` block, the program execution returns to the normal flow.You can also handle more than one ...
def loan_emi(amount, duration, rate, down_payment=0): loan_amount = amount - down_payment try: emi = loan_amount * rate * ((1+rate)**duration) / (((1+rate)**duration)-1) except ZeroDivisionError: emi = loan_amount / duration emi = math.ceil(emi) return emi
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
We can use the updated `loan_emi` function to solve our problem.> **Q**: If you borrow `$100,000` using a 10-year loan with an interest rate of 9% per annum, what is the total amount you end up paying as interest?
emi_with_interest = loan_emi(amount=100000, duration=10*12, rate=0.09/12) emi_with_interest emi_without_interest = loan_emi(amount=100000, duration=10*12, rate=0) emi_without_interest total_interest = (emi_with_interest - emi_without_interest) * 10*12 print("The total interest paid is ${}.".format(total_interest))
The total interest paid is $51960.
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Documenting functions using DocstringsWe can add some documentation within our function using a *docstring*. A docstring is simply a string that appears as the first statement within the function body, and is used by the `help` function. A good docstring describes what the function does, and provides some explanation ...
def loan_emi(amount, duration, rate, down_payment=0): """Calculates the equal montly installment (EMI) for a loan. Arguments: amount - Total amount to be spent (loan + down payment) duration - Duration of the loan (in months) rate - Rate of interest (monthly) down_payment (o...
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MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
In the docstring above, we've provided some additional information that the `duration` and `rate` are measured in months. You might even consider naming the arguments `duration_months` and `rate_monthly`, to avoid any confusion whatsoever. Can you think of some other ways to improve the function?
help(loan_emi)
Help on function loan_emi in module __main__: loan_emi(amount, duration, rate, down_payment=0) Calculates the equal montly installment (EMI) for a loan. Arguments: amount - Total amount to be spent (loan + down payment) duration - Duration of the loan (in months) rate - Rate of int...
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Exercise - Data Analysis for Vacation PlanningYou're planning a vacation, and you need to decide which city you want to visit. You have shortlisted four cities and identified the return flight cost, daily hotel cost, and weekly car rental cost. While renting a car, you need to pay for entire weeks, even if you return ...
# Use these cells to answer the question - build the function step-by-step paris_dict = dict(city="Paris", cost_return_flight=200, cost_hotel_per_night=20, cost_car_rental_weekly=200) london_dict = dict(city="London", cost_return_flight=250, cost_hotel_per_night=30, cost_car_rental_weekly=120) dubai_dict = dict(city="D...
(1140, 17, 3) (910, 14, 2) (850, 16, 3) (1430, 49, 7)
MIT
src/Next Steps with Python/.ipynb_checkpoints/Writing Reusable Code using Functions in Python-checkpoint.ipynb
sahanashetty31/Data-Analysis-with-Python-Zero-to-Pandas
Region MaskingIn last excersize we were able to identify lane lines but that is not enough because there were many more objects/pixels we identified and they were not all lane lines.In this notebook, lets define the region of interest and identify lane lines from there. Its basically a way to make sure your camera see...
import matplotlib.pyplot as plt import matplotlib.image as mpimg import numpy as np image = mpimg.imread('../img/test.jpg') print('This image is: ', type(image), 'with dimensions:', image.shape) # Pull out the x and y sizes and make a copy of the image ysize = image.shape[0] xsize = image.shape[1] region_se...
This image is: <class 'numpy.ndarray'> with dimensions: (540, 960, 3)
MIT
01-Computer-Vision-Fundamentals/.ipynb_checkpoints/2 Region Masking-checkpoint.ipynb
vyasparthm/AutonomousDriving
Masking the ImageNow that we have been able to pick threshold colors in last quiz, let's go one step further and mark the region of interest in the given image.
import matplotlib.pyplot as plt import matplotlib.image as mpimg import numpy as np image = mpimg.imread('../img/test.jpg') print('This image is: ', type(image), 'with dimensions:', image.shape) # Pull out the x and y sizes and make a copy of the image ysize = image.shape[0] xsize = image.shape[1] region_se...
This image is: <class 'numpy.ndarray'> with dimensions: (540, 960, 3)
MIT
01-Computer-Vision-Fundamentals/.ipynb_checkpoints/2 Region Masking-checkpoint.ipynb
vyasparthm/AutonomousDriving
Modeling and Simulation in PythonChapter 3Copyright 2017 Allen DowneyLicense: [Creative Commons Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0)
# Configure Jupyter so figures appear in the notebook %matplotlib inline # Configure Jupyter to display the assigned value after an assignment %config InteractiveShell.ast_node_interactivity='last_expr_or_assign' # import functions from the modsim library from modsim import * # set the random number generator np.ran...
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
More than one State objectHere's the code from the previous chapter, with two changes:1. I've added DocStrings that explain what each function does, and what parameters it takes.2. I've added a parameter named `state` to the functions so they work with whatever `State` object we give them, instead of always using `bik...
def step(state, p1, p2): """Simulate one minute of time. state: bikeshare State object p1: probability of an Olin->Wellesley customer arrival p2: probability of a Wellesley->Olin customer arrival """ if flip(p1): bike_to_wellesley(state) if flip(p2): bike_to_olin(st...
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
And here's `run_simulation`, which is a solution to the exercise at the end of the previous notebook.
def run_simulation(state, p1, p2, num_steps): """Simulate the given number of time steps. state: State object p1: probability of an Olin->Wellesley customer arrival p2: probability of a Wellesley->Olin customer arrival num_steps: number of time steps """ results = TimeSeries() f...
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Now we can create more than one `State` object:
bikeshare1 = State(olin=10, wellesley=2) bikeshare2 = State(olin=2, wellesley=10)
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Whenever we call a function, we indicate which `State` object to work with:
bike_to_olin(bikeshare1) bike_to_wellesley(bikeshare2)
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
And you can confirm that the different objects are getting updated independently:
bikeshare1 bikeshare2
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Negative bikes In the code we have so far, the number of bikes at one of the locations can go negative, and the number of bikes at the other location can exceed the actual number of bikes in the system.If you run this simulation a few times, it happens often.
bikeshare = State(olin=10, wellesley=2) run_simulation(bikeshare, 0.4, 0.2, 60) decorate_bikeshare()
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
We can fix this problem using the `return` statement to exit the function early if an update would cause negative bikes.
def bike_to_wellesley(state): """Move one bike from Olin to Wellesley. state: bikeshare State object """ if state.olin == 0: return state.olin -= 1 state.wellesley += 1 def bike_to_olin(state): """Move one bike from Wellesley to Olin. state: bikeshare State object ...
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Now if you run the simulation again, it should behave.
bikeshare = State(olin=10, wellesley=2) run_simulation(bikeshare, 0.4, 0.2, 60) decorate_bikeshare()
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Comparison operators The `if` statements in the previous section used the comparison operator `==`. The other comparison operators are listed in the book.It is easy to confuse the comparison operator `==` with the assignment operator `=`.Remember that `=` creates a variable or gives an existing variable a new value.
x = 5
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Whereas `==` compares two values and returns `True` if they are equal.
x == 5
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
You can use `==` in an `if` statement.
if x == 5: print('yes, x is 5')
yes, x is 5
MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
But if you use `=` in an `if` statement, you get an error.
# If you remove the # from the if statement and run it, you'll get # SyntaxError: invalid syntax #if x = 5: # print('yes, x is 5')
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
**Exercise:** Add an `else` clause to the `if` statement above, and print an appropriate message.Replace the `==` operator with one or two of the other comparison operators, and confirm they do what you expect. Metrics Now that we have a working simulation, we'll use it to evaluate alternative designs and see how good...
bikeshare = State(olin=10, wellesley=2, olin_empty=0, wellesley_empty=0)
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Next we need versions of `bike_to_wellesley` and `bike_to_olin` that update the metrics.
def bike_to_wellesley(state): """Move one bike from Olin to Wellesley. state: bikeshare State object """ if state.olin == 0: state.olin_empty += 1 return state.olin -= 1 state.wellesley += 1 def bike_to_olin(state): """Move one bike from Wellesley to Olin. ...
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Now when we run a simulation, it keeps track of unhappy customers.
run_simulation(bikeshare, 0.4, 0.2, 60) decorate_bikeshare()
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
After the simulation, we can print the number of unhappy customers at each location.
bikeshare.olin_empty bikeshare.wellesley_empty
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Exercises**Exercise:** As another metric, we might be interested in the time until the first customer arrives and doesn't find a bike. To make that work, we have to add a "clock" to keep track of how many time steps have elapsed:1. Create a new `State` object with an additional state variable, `clock`, initialized to...
bikeshare = State(olin=10, wellesley=2, olin_empty=0, wellesley_empty=0, clock=0) # Solution def step(state, p1, p2): """Simulate one minute of time. state: bikeshare State object p1: probability of an Olin->Wellesley customer arrival p2: probability of a Welle...
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
**Exercise:** Continuing the previous exercise, let's record the time when the first customer arrives and doesn't find a bike.1. Create a new `State` object with an additional state variable, `t_first_empty`, initialized to -1 as a special value to indicate that it has not been set. 2. Write a modified version of `step...
# Solution bikeshare = State(olin=10, wellesley=2, olin_empty=0, wellesley_empty=0, clock=0, t_first_empty=-1) # Solution def step(state, p1, p2): """Simulate one minute of time. state: bikeshare State object p1: probability of an Olin->Wellesley customer arrival ...
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MIT
soln/chap03soln.ipynb
pmalo46/ModSimPy
Tutorial: PyTorch
__author__ = "Ignacio Cases" __version__ = "CS224u, Stanford, Spring 2021"
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Contents1. [Motivation](Motivation)1. [Importing PyTorch](Importing-PyTorch)1. [Tensors](Tensors) 1. [Tensor creation](Tensor-creation) 1. [Operations on tensors](Operations-on-tensors)1. [GPU computation](GPU-computation)1. [Neural network foundations](Neural-network-foundations) 1. [Automatic differentiation](Aut...
import torch
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
**Side note**: why not `import pytorch`? The name of the package is `torch` for historical reasons: `torch` is the orginal name of the ancestor of the PyTorch library that got started back in 2002 as a C library with Lua scripting. It was only much later that the original `torch` was ported to Python. The PyTorch proje...
print("PyTorch version {}".format(torch.__version__)) print("GPU-enabled installation? {}".format(torch.cuda.is_available()))
PyTorch version 1.8.0 GPU-enabled installation? False
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
PyTorch has good [documentation](https://pytorch.org/docs/stable/index.html) but it can take some time to familiarize oneself with the structure of the package; it's worth the effort to do so!We will also make use of other imports:
import numpy as np
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Tensors Tensors collections of numbers represented as an array, and are the basic building blocks in PyTorch.You are probably already familiar with several types of tensors: - A scalar, a single number, is a zero-th order tensor. - A column vector $v$ of dimensionality $d_c \times 1$ is a tensor of order 1. -...
t = torch.FloatTensor(2, 3) print(t) print(t.size())
tensor([[9.8091e-45, 0.0000e+00, 0.0000e+00], [0.0000e+00, 0.0000e+00, 0.0000e+00]]) torch.Size([2, 3])
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Note that we specified the dimensions as the arguments to the constructor by passing the numbers directly – and not a list or a tuple, which would have very different outcomes as we will see below! We can always inspect the size of the tensor using the `size()` method.The constructor method allocates space in memory fo...
t.zero_()
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
The underscore after the method name is important: it means that the operation happens _in place_: the returned object is the same object but now with different content. A very handy way to construct a tensor using the constructor happens when we have available the content we want to put in the tensor in the form of a ...
torch.FloatTensor([[1, 2, 3], [4, 5, 6]])
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Calling a method in the torch module A very convenient way to create tensors, in addition to using the constructor method, is to use one of the multiple methods provided in the `torch` module. In particular, the `tensor` method allows us to pass a number or iterable as the argument to get the appropriately typed tenso...
tl = torch.tensor([1, 2, 3]) t = torch.tensor([1., 2., 3.]) print("A 64-bit integer tensor: {}, {}".format(tl, tl.type())) print("A 32-bit float tensor: {}, {}".format(t, t.type()))
A 64-bit integer tensor: tensor([1, 2, 3]), torch.LongTensor A 32-bit float tensor: tensor([1., 2., 3.]), torch.FloatTensor
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
We can create a similar 2x3 tensor to the one above by using the `torch.zeros()` method, passing a sequence of dimensions to it:
t = torch.zeros(2, 3) print(t)
tensor([[0., 0., 0.], [0., 0., 0.]])
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
There are many methods for creating tensors. We list some useful ones:
t_zeros = torch.zeros_like(t) # zeros_like returns a new tensor t_ones = torch.ones(2, 3) # creates a tensor with 1s t_fives = torch.empty(2, 3).fill_(5) # creates a non-initialized tensor and fills it with 5 t_random = torch.rand(2, 3) # creates a uniform random tensor t_normal = torch.randn...
tensor([[0., 0., 0.], [0., 0., 0.]]) tensor([[1., 1., 1.], [1., 1., 1.]]) tensor([[5., 5., 5.], [5., 5., 5.]]) tensor([[0.2930, 0.9685, 0.0458], [0.9844, 0.1271, 0.2497]]) tensor([[-0.4341, 0.1566, -0.7059], [ 0.5371, 0.0399, 0.5803]])
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
We now see emerging two important paradigms in PyTorch. The _imperative_ approach to performing operations, using _inplace_ methods, is in marked contrast with an additional paradigm also used in PyTorch, the _functional_ approach, where the returned object is a copy of the original object. Both paradigms have their sp...
# creates a new copy of the tensor that is still linked to # the computational graph (see below) t1 = torch.clone(t) assert id(t) != id(t1), 'Functional methods create a new copy of the tensor' # To create a new _independent_ copy, we do need to detach # from the graph t1 = torch.clone(t).detach()
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Using the PyTorch–NumPy bridge A quite useful feature of PyTorch is its almost seamless integration with NumPy, which allows us to perform operations on NumPy and interact from PyTorch with the large number of NumPy libraries as well. Converting a NumPy multi-dimensional array into a PyTorch tensor is very simple: we ...
# Create a new multi-dimensional array in NumPy with the np datatype (np.float32) a = np.array([1., 2., 3.]) # Convert the array to a torch tensor t = torch.tensor(a) print("NumPy array: {}, type: {}".format(a, a.dtype)) print("Torch tensor: {}, type: {}".format(t, t.dtype))
NumPy array: [1. 2. 3.], type: float64 Torch tensor: tensor([1., 2., 3.], dtype=torch.float64), type: torch.float64
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
We can also seamlessly convert a PyTorch tensor into a NumPy array:
t.numpy()
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
**Side note**: why not `torch.from_numpy(a)`? The `from_numpy()` method is depecrated in favor of `tensor()`, which is a more capable method in the torch package. `from_numpy()` is only there for backwards compatibility. It can be a little bit quirky, so I recommend using the newer method in PyTorch >= 0.4. Indexing I...
t = torch.randn(2, 3) t[ : , 0]
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
PyTorch also supports indexing using long tensors, for example:
t = torch.randn(5, 6) print(t) i = torch.tensor([1, 3]) j = torch.tensor([4, 5]) print(t[i]) # selects rows 1 and 3 print(t[i, j]) # selects (1, 4) and (3, 5)
tensor([[ 0.0421, 0.0713, -2.1790, 0.3855, 1.8714, -0.2528], [-0.3344, 0.8028, -0.2878, -0.2721, 1.0514, -1.3336], [-1.3506, 0.5657, 1.4540, -0.7039, -0.6878, 0.9614], [ 0.3845, 0.4493, -0.8910, -1.4512, 0.1300, 1.5551], [ 0.9192, 0.3812, -1.3167, 0.4005, -0.0778, 1.5110]])...
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Type conversion Each tensor has a set of convenient methods to convert types. For example, if we want to convert the tensor above to a 32-bit float tensor, we use the method `.float()`:
t = t.float() # converts to 32-bit float print(t) t = t.double() # converts to 64-bit float print(t) t = t.byte() # converts to unsigned 8-bit integer print(t)
tensor([[ 0.0421, 0.0713, -2.1790, 0.3855, 1.8714, -0.2528], [-0.3344, 0.8028, -0.2878, -0.2721, 1.0514, -1.3336], [-1.3506, 0.5657, 1.4540, -0.7039, -0.6878, 0.9614], [ 0.3845, 0.4493, -0.8910, -1.4512, 0.1300, 1.5551], [ 0.9192, 0.3812, -1.3167, 0.4005, -0.0778, 1.5110]])...
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Operations on tensors Now that we know how to create tensors, let's create some of the fundamental tensors and see some common operations on them:
# Scalars =: creates a tensor with a scalar # (zero-th order tensor, i.e. just a number) s = torch.tensor(42) print(s)
tensor(42)
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
**Tip**: a very convenient to access scalars is with `.item()`:
s.item()
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Let's see higher-order tensors – remember we can always inspect the dimensionality of a tensor using the `.size()` method:
# Row vector x = torch.randn(1,3) print("Row vector\n{}\nwith size {}".format(x, x.size())) # Column vector v = torch.randn(3,1) print("Column vector\n{}\nwith size {}".format(v, v.size())) # Matrix A = torch.randn(3, 3) print("Matrix\n{}\nwith size {}".format(A, A.size()))
Row vector tensor([[ 1.5811, -0.0148, -2.1993]]) with size torch.Size([1, 3]) Column vector tensor([[-0.5085], [ 1.1261], [ 0.2023]]) with size torch.Size([3, 1]) Matrix tensor([[-1.6138, 0.5316, -0.6007], [ 0.8608, -0.9427, 0.0111], [-0.7028, -1.2223, 1.1992]]) with size torch.Size([...
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
A common operation is matrix-vector multiplication (and in general tensor-tensor multiplication). For example, the product $\mathbf{A}\mathbf{v} + \mathbf{b}$ is as follows:
u = torch.matmul(A, v) print(u) b = torch.randn(3,1) y = u + b # we can also do torch.add(u, b) print(y)
tensor([[ 1.2978], [-1.4971], [-0.7765]]) tensor([[ 0.6784], [-2.1156], [ 0.5897]])
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
where we retrieve the expected result (a column vector of dimensions 3x1). We can of course compose operations:
s = torch.matmul(x, torch.matmul(A, v)) print(s.item())
3.781867027282715
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
There are many functions implemented for every tensor, and we encourage you to study the documentation. Some of the most common ones:
# common tensor methods (they also have the counterpart in # the torch package, e.g. as torch.sum(t)) t = torch.randn(2,3) t.sum(dim=0) t.t() # transpose t.numel() # number of elements in tensor t.nonzero() # indices of non-zero elements t.view(-1, 2) # reorganizes ...
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
GPU computation Deep Learning frameworks take advantage of the powerful computational capabilities of modern graphic processing units (GPUs). GPUs were originally designed to perform frequent operations for graphics very efficiently and fast, such as linear algebra operations, which makes them ideal for our interests....
try: t_gpu = torch.cuda.FloatTensor(3, 3) # creation of a GPU tensor t_gpu.zero_() # initialization to zero except TypeError as err: print(err)
type torch.cuda.FloatTensor not available. Torch not compiled with CUDA enabled.
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
However, a more common approach that gives us flexibility is through the use of devices. A device in PyTorch refers to either the CPU (indicated by the string "cpu") or one of the possible GPU cards in the machine (indicated by the string "cuda:$n$", where $n$ is the index of the card). Let's create a random gaussian m...
try: t_gpu = torch.randn(3, 3, device="cuda:0") except AssertionError as err: print(err) t_gpu = None t_gpu
Torch not compiled with CUDA enabled
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
As you can notice, the tensor now has the explicit device set to be a CUDA device, not a CPU device. Let's now create a tensor in the CPU and move it to the GPU:
# we could also state explicitly the device to be the # CPU with torch.randn(3,3,device="cpu") t = torch.randn(3, 3) t
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
In this case, the device is the CPU, but PyTorch does not explicitly say that given that this is the default behavior. To copy the tensor to the GPU we use the `.to()` method that every tensor implements, passing the device as an argument. This method creates a copy in the specified device or, if the tensor already res...
try: t_gpu = t.to("cuda:0") # copies the tensor from CPU to GPU # note that if we do now t_to_gpu.to("cuda:0") it will # return the same tensor without doing anything else # as this tensor already resides on the GPU print(t_gpu) print(t_gpu.device) except AssertionError as err: print(err)
Torch not compiled with CUDA enabled
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
**Tip**: When we program PyTorch models, we will have to specify the device in several places (not so many, but definitely more than once). A good practice that is consistent accross the implementation and makes the code more portable is to declare early in the code a device variable by querying the framework if there ...
device = torch.device("cuda:0") if torch.cuda.is_available() else torch.device("cpu") print(device)
cpu
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
We can then use `device` as an argument of the `.to()` method in the rest of our code:
# moves t to the device (this code will **not** fail if the # local machine has not access to a GPU) t.to(device)
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
**Side note**: having good GPU backend support is a critical aspect of a deep learning framework. Some models depend crucially on performing computations on a GPU. Most frameworks, including PyTorch, only provide good support for GPUs manufactured by Nvidia. This is mostly due to the heavy investment this company made ...
import torch.nn as nn
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
All our models subclass this base `nn.Module` class, which provides an interface to important methods used for constructing and working with our models, and which contains sensible initializations for our models. Modules can contain other modules (and usually do).Let's see a simple, custom implementation of a multi-lay...
class MyCustomModule(nn.Module): def __init__(self, n_inputs, n_hidden, n_output_classes): # call super to initialize the class above in the hierarchy super(MyCustomModule, self).__init__() # first affine transformation self.W = nn.Linear(n_inputs, n_hidden) # non-linearity (...
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Then, we can use our new module as follows:
# set the network's architectural parameters n_inputs = 3 n_hidden= 4 n_output_classes = 2 # instantiate the model model = MyCustomModule(n_inputs, n_hidden, n_output_classes) # create a simple input tensor # size is [1,3]: a mini-batch of one example, # this example having dimension 3 x = torch.FloatTensor([[0.3, 0....
tensor([[0.2473, 0.1775]], grad_fn=<AddmmBackward>)
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
As we see, the output is a tensor with its gradient function attached – Autograd tracks it for us. **Tip**: modules overrides the `__call__()` method, where the framework does some work. Thus, instead of directly calling the `forward()` method, we apply the input to the model instead. Sequential A powerful class in th...
class MyCustomModule(nn.Module): def __init__(self, n_inputs, n_hidden, n_output_classes): super(MyCustomModule, self).__init__() self.network = nn.Sequential( nn.Linear(n_inputs, n_hidden), nn.ReLU(), nn.Linear(n_hidden, n_output_classes)) def forward(self, ...
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
As you can imagine, this can be handy when we have a large number of layers for which the actual names are not that meaningful. It also improves readability:
class MyCustomModule(nn.Module): def __init__(self, n_inputs, n_hidden, n_output_classes): super(MyCustomModule, self).__init__() self.p_keep = 0.7 self.network = nn.Sequential( nn.Linear(n_inputs, n_hidden), nn.ReLU(), nn.Linear(n_hidden, 2*n_hidden), ...
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
**Side note**: Another important package in `torch.nn` is `Functional`, typically imported as `F`. Functional contains many useful functions, from non-linear activations to convolutional, dropout, and even distance functions. Many of these functions have counterpart implementations as layers in the `nn` package so that...
import torch.nn.functional as F y = F.relu(torch.FloatTensor([[-5, -1, 0, 5]])) y
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Criteria and loss functions PyTorch has implementations for the most common criteria in the `torch.nn` package. You may notice that, as with many of the other functions, there are two implementations of loss functions: the reference functions in `torch.nn.functional` and practical class in `torch.nn`, which are the on...
# the true label (in this case, 2) from our dataset wrapped # as a tensor of minibatch size of 1 y_gold = torch.tensor([1]) # our simple classification criterion for this simple example criterion = nn.CrossEntropyLoss() # forward pass of our model (remember, using apply instead of forward) y = model(x) # apply the c...
tensor(0.7287, grad_fn=<NllLossBackward>)
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Optimization Once we have computed the loss for a training example or minibatch of examples, we update the parameters of the model guided by the information contained in the gradient. The role of updating the parameters belongs to the optimizer, and PyTorch has a number of implementations available right away – and if...
import torch import torch.nn as nn import torch.nn.functional as F import torch.utils.data as data import numpy as np import matplotlib.pyplot as plt import math
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Early on the code, we define the device that we want to use:
device = torch.device("cuda:0") if torch.cuda.is_available() else torch.device("cpu")
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tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Let's fix $a=1$, $\phi=1$ and generate traning data in the interval $x \in [0,2\pi)$ using NumPy:
M = 1200 # sample from the x axis M points x = np.random.rand(M) * 2*math.pi # add noise eta = np.random.rand(M) * 0.01 # compute the function y = np.sin(x) + eta # plot _ = plt.scatter(x,y) # use the NumPy-PyTorch bridge x_train = torch.tensor(x[0:1000]).float().view(-1, 1).to(device) y_train = torch.tensor(y[0:10...
0.005281522491713986
Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Reproducibility
def enforce_reproducibility(seed=42): # Sets seed manually for both CPU and CUDA torch.manual_seed(seed) # For atomic operations there is currently # no simple way to enforce determinism, as # the order of parallel operations is not known. # # CUDNN torch.backends.cudnn.deterministic = T...
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Apache-2.0
tutorial_pytorch.ipynb
feifang24/cs224u-spr2021
Default exception blockHandle any type off exception
enter first no5 enter second now error occured end
MIT
mod_07/mod_07_01.ipynb
merazlab/python
Single try with multiple except block
try: x = int(input("enter first no")) y = int(input("enter second no")) z = x / y print("result", z) except(ZeroDivisionError): print("second value is not zero") except(ValueError): print("Value eroor") except: print("error occured") print("end")
enter first no7 enter second nof Value eroor end
MIT
mod_07/mod_07_01.ipynb
merazlab/python
Raise exception-Default exception block is last block always
try: x = int(input("enter first no")) y = int(input("enter second no")) z = x / y print("result", z) raise KeyError except(ZeroDivisionError): print("second value is not zero") except(ValueError): print("Value eroor") except: print("error occured") print("end")
enter first no4 enter second no3 result 1.3333333333333333 error occured end
MIT
mod_07/mod_07_01.ipynb
merazlab/python
finally The sets of statements which are compulsary to exectute whether exception is raised or not raisedException- Only user frienly statement Resource releasing statemnet are written in finally group
try: x = int(input("enter first no")) y = int(input("enter second no")) z = x / y print("result", z) except(ZeroDivisionError): print("second value is not zero") finally: #run exception raised or not raised print("bye") print("end") x = open("myfile.txt") print(x.read()) x.write("meraz") x.close() print(...
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MIT
mod_07/mod_07_01.ipynb
merazlab/python
How to create Popups Simple popupsYou can define your popup at the feature creation, but you can also overwrite them afterwards:
import folium m = folium.Map([45, 0], zoom_start=4) folium.Marker([45, -30], popup="inline implicit popup").add_to(m) folium.CircleMarker( location=[45, -10], radius=25, fill=True, popup=folium.Popup("inline explicit Popup"), ).add_to(m) ls = folium.PolyLine( locations=[[43, 7], [43, 13], [47, ...
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MIT
examples/Popups.ipynb
uni-3/folium
Vega PopupYou may know that it's possible to create awesome Vega charts with (or without) `vincent`. If you're willing to put one inside a popup, it's possible thanks to `folium.Vega`.
import json import numpy as np import vincent scatter_points = { "x": np.random.uniform(size=(100,)), "y": np.random.uniform(size=(100,)), } # Let's create the vincent chart. scatter_chart = vincent.Scatter(scatter_points, iter_idx="x", width=600, height=300) # Let's convert it to JSON. scatter_json = scatt...
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MIT
examples/Popups.ipynb
uni-3/folium