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This program will read the input lines in where.data and for each line check to see if it is already in the database.
If we don’t have the ----- Figure 16.1: A Google Map data for the location, it will call the geocoding API to retrieve the data and store it in the database. Here is a sample run after there is already some data in the database: Found in database Northeastern University Found in database University of Hong Kong, ...
} Resolving Kokshetau Institute of Economics and Management Retrieving http://maps.googleapis.com/maps/api/ geocode/json?sensor=false&address=Kokshetau+Inst ... Retrieved 1749 characters { "results" : [ {'status': 'OK', 'results': ...
} ... The first five locations are already in the database and so they are skipped.
The program scans to the point where it finds new locations and starts retrieving them. ----- The geoload.py program can be stopped at any time, and there is a counter that you can use to limit the number of calls to the geocoding API for each run.
Given that the where.data only has a few hundred data items, you should not run into the daily rate limit, but if you had more data it might take several runs over several days to get your database to have all of the geocoded data for your input. Once you have some data loaded into geodata.sqlite, you can visualize th...
This program reads the database and writes the file where.js with the location, latitude, and longitude in the form of executable JavaScript code. A run of the geodump.py program is as follows: Northeastern University, ...
Boston, MA 02115, USA 42.3396998 -71.08975 Bradley University, 1501 ...
Peoria, IL 61625, USA 40.6963857 -89.6160811 ... Technion, Viazman 87, Kesalsaba, 32000, Israel 32.7775 35.0216667 Monash University Clayton ...
VIC 3800, Australia -37.9152113 145.134682 Kokshetau, Kazakhstan 53.2833333 69.3833333 ... 12 records written to where.js Open where.html to view the data in a browser The file where.html consists of HTML and JavaScript to visualize a Google map. It reads the most recent data in where.js to get the data to be visualiz...
Here is the format of the where.js file: myData = [ [42.3396998,-71.08975, 'Northeastern Uni ... Boston, MA 02115'], [40.6963857,-89.6160811, 'Bradley University, ...
Peoria, IL 61625, USA'], [32.7775,35.0216667, 'Technion, Viazman 87, Kesalsaba, 32000, Israel'], ... ]; This is a JavaScript variable that contains a list of lists.
The syntax for JavaScript list constants is very similar to Python, so the syntax should be familiar to you. Simply open where.html in a browser to see the locations.
You can hover over each map pin to find the location that the geocoding API returned for the user-entered input.
If you cannot see any data when you open the where.html file, you might want to check the JavaScript or developer console for your browser. ##### 16.2 Visualizing networks and interconnections In this application, we will perform some of the functions of a search engine.
We will first spider a small subset of the web and run a simplified version of the Google page rank algorithm to determine which pages are most highly connected, and then visualize the page rank and connectivity of our small corner of the web. [We will use the D3 JavaScript visualization library http://d3js.org/ to pro...
You can restart the process at any time by removing the spider.sqlite file and rerunning spider.py. Enter web url or enter: http://www.dr-chuck.com/ ['http://www.dr-chuck.com'] How many pages:2 1 http://www.dr-chuck.com/ 12 2 http://www.dr-chuck.com/csev-blog/ 57 How many pages: In this sample run, we told it to cra...
If you restart the program and tell it to crawl more pages, it will not re-crawl any pages already in the database. Upon restart it goes to a random non-crawled page and starts there.
So each successive run of spider.py is additive. Enter web url or enter: http://www.dr-chuck.com/ ['http://www.dr-chuck.com'] How many pages:3 3 http://www.dr-chuck.com/csev-blog 57 4 http://www.dr-chuck.com/dr-chuck/resume/speaking.htm 1 5 http://www.dr-chuck.com/dr-chuck/resume/index.htm 13 How many pages: You can...
The spider chooses randomly amongst all non-visited links across all the webs as the next page to spider. If you want to dump the contents of the spider.sqlite file, you can run spdump.py as follows: (5, None, 1.0, 3, 'http://www.dr-chuck.com/csev-blog') (3, None, 1.0, 4, 'http://www.dr-chuck.com/dr-chuck/resume/spea...
The spdump.py program only shows pages that have at least one incoming link to them. Once you have a few pages in the database, you can run page rank on the pages using the sprank.py program.
You simply tell it how many page rank iterations to run. How many iterations:2 1 0.546848992536 2 0.226714939664 [(1, 0.559), (2, 0.659), (3, 0.985), (4, 2.135), (5, 0.659)] You can dump the database again to see that page rank has been updated: (5, 1.0, 0.985, 3, 'http://www.dr-chuck.com/csev-blog') (3, 1.0, 2.135...
You can even run sprank.py a few times and then go spider a few more pages sith spider.py and then run sprank.py to reconverge the page rank values.
A search engine usually runs both the crawling and ranking programs all the time. If you want to restart the page rank calculations without respidering the web pages, you can use spreset.py and then restart sprank.py. How many iterations:50 1 0.546848992536 2 0.226714939664 3 0.0659516187242 4 0.0244199333 5 0.010209...
The network initially is quite unbalanced and so the individual page rank values change wildly between iterations. But in a few short iterations, the page rank converges.
You should run prank.py long enough that the page rank values converge. If you want to visualize the current top pages in terms of page rank, run spjson.py to read the database and write the data for the most highly linked pages in JSON format to be viewed in a web browser. Creating JSON output on spider.json... How ...
30 Open force.html in a browser to view the visualization You can view this data by opening the file force.html in your web browser. This shows an automatic layout of the nodes and links.
You can click and drag any node and you can also double-click on a node to find the URL that is represented by the node. If you rerun the other utilities, rerun spjson.py and press refresh in the browser to get the new data from spider.json. ##### 16.3 Visualizing mail data Up to this point in the book, you have bec...
Now it is time to take our analysis of email data_ to the next level. In the real world, sometimes you have to pull down mail data from servers.
That might take quite some time and the data might be inconsistent, error-filled, and need a lot of cleanup or adjustment.
In this section, we work with an application that is the most complex so far and pull down nearly a gigabyte of data and visualize it. You can download this application from: [www.pythonlearn.com/code3/gmane.zip](http://www.pythonlearn.com/code3/gmane.zip) [We will be using data from a free email list archiving serv...
They also have a very liberal policy regarding accessing their data through their API. They have no rate limits, but ask that you don’t overload their service and take only the data you need.
You can read gmane’s terms and conditions at this page: ----- Figure 16.3: A Word Cloud from the Sakai Developer List [http://gmane.org/export.php](http://gmane.org/export.php) _It is very important that you make use of the gmane.org data responsibly by adding_ _delays to your access of their services and spreadin...
Do not abuse this free service and ruin it for the rest of us._ When the Sakai email data was spidered using this software, it produced nearly a Gigabyte of data and took a number of runs on several days.
The file README.txt in the above ZIP may have instructions as to how you can download a pre-spidered copy of the content.sqlite file for a majority of the Sakai email corpus so you don’t have to spider for five days just to run the programs.
If you download the prespidered content, you should still run the spidering process to catch up with more recent messages. The first step is to spider the gmane repository.
The base URL is hard-coded in the _gmane.py and is hard-coded to the Sakai developer list. You can spider another_ repository by changing that base url.
Make sure to delete the content.sqlite file if you switch the base url. The gmane.py file operates as a responsible caching spider in that it runs slowly and retrieves one mail message per second so as to avoid getting throttled by gmane. It stores all of its data in a database and can be interrupted and restarted as ...
It may take many hours to pull all the data down.
So you may need to restart several times. Here is a run of gmane.py retrieving the last five messages of the Sakai developer list: How many messages:10 ----- http://download.gmane.org/gmane.comp.cms.sakai.devel/51410/51411 9460 nealcaidin@sakaifoundation.org 2013-04-05 re: [building ... http://download.gmane.org/g...
It continues spidering until it has spidered the desired number of messages or it reaches a page that does not appear to be a properly formatted message. Sometimes gmane.org is missing a message.
Perhaps administrators can delete messages or perhaps they get lost.
If your spider stops, and it seems it has hit a missing message, go into the SQLite Manager and add a row with the missing id leaving all the other fields blank and restart gmane.py.
This will unstick the spidering process and allow it to continue.
These empty messages will be ignored in the next phase of the process. One nice thing is that once you have spidered all of the messages and have them in content.sqlite, you can run gmane.py again to get new messages as they are sent to the list. The content.sqlite data is pretty raw, with an inefficient data model, ...
This is intentional as it allows you to look at content.sqlite in the SQLite Manager to debug problems with the spidering process.
It would be a bad idea to run any queries against this database, as they would be quite slow. The second process is to run the program gmodel.py.
This program reads the raw data from content.sqlite and produces a cleaned-up and well-modeled version of the data in the file index.sqlite.
This file will be much smaller (often 10X smaller) than content.sqlite because it also compresses the header and body text. Each time gmodel.py runs it deletes and rebuilds index.sqlite, allowing you to adjust its parameters and edit the mapping tables in content.sqlite to tweak the data cleaning process.
This is a sample run of gmodel.py.
It prints a line out each time 250 mail messages are processed so you can see some progress happening, as this program may run for a while processing nearly a Gigabyte of mail data. Loaded allsenders 1588 and mapping 28 dns mapping 1 1 2005-12-08T23:34:30-06:00 ggolden22@mac.com 251 2005-12-22T10:03:20-08:00 tpamsler@...
Other domain names are truncated to three levels. So si.umich.edu becomes umich.edu and caret.cam.ac.uk becomes cam.ac.uk.
Email addresses are also forced to lower case, and some of the @gmane.org address like the following arwhyte-63aXycvo3TyHXe+LvDLADg@public.gmane.org are converted to the real address whenever there is a matching real email address elsewhere in the message corpus. In the content.sqlite database there are two tables t...
For example, Steve Githens used the following email addresses as he changed jobs over the life of the Sakai developer list: s-githens@northwestern.edu sgithens@cam.ac.uk swgithen@mtu.edu We can add two entries to the Mapping table in content.sqlite so gmodel.py will map all three to one address: s-githens@northweste...
The following mapping was added to the Sakai data: iupui.edu -> indiana.edu so all the accounts from the various Indiana University campuses are tracked together. You can rerun the gmodel.py over and over as you look at the data, and add mappings to make the data cleaner and cleaner.
When you are done, you will have a nicely indexed version of the email in index.sqlite. This is the file to use to do data analysis.
With this file, data analysis will be really quick. The first, simplest data analysis is to determine “who sent the most mail?” and “which organization sent the most mail”?
This is done using gbasic.py: How many to dump?
5 Loaded messages= 51330 subjects= 25033 senders= 1584 Top 5 Email list participants steve.swinsburg@gmail.com 2657 azeckoski@unicon.net 1742 ieb@tfd.co.uk 1591 csev@umich.edu 1304 david.horwitz@uct.ac.za 1184 ----- Top 5 Email list organizations gmail.com 7339 umich.edu 6243 uct.ac.za 2451 indiana.edu 2258 unicon....
If you have a lot of data to manage, a multistep process like the one in this application may take a little longer to develop, but will save you a lot of time when you really start to explore and visualize your data. You can produce a simple visualization of the word frequency in the subject lines in the file gword.py...
It computes email participation by organizations over time. Loaded messages= 51330 subjects= 25033 senders= 1584 Top 10 Oranizations ['gmail.com', 'umich.edu', 'uct.ac.za', 'indiana.edu', 'unicon.net', 'tfd.co.uk', 'berkeley.edu', 'longsight.com', 'stanford.edu', 'ox.ac.uk'] Output written to gline.js Its output is ...
How does understanding the Big O notation help in handling big data? Big O notation is like gauging the size of a crowd at an event to determine how much food and space you need. It helps predict how well your algorithm will perform as the size of your data grows.
What is an 'if statement'? An 'if statement' works like a road sign decision. If the condition is true, you take one turn; otherwise, you continue straight or take a different turn
How do conditionals work in Python? Conditionals in Python are like road signs, directing the flow of traffic (data). if-elif-else statements help the program decide which path to take based on certain conditions
What are if, elif, and else statements? These statements are like checkpoints in a video game. if checks a condition: if it’s true, it does something. elif (else if) checks another condition if the first isn't true. else does something else if none of the conditions are true.
What does a Boolean value represent? A Boolean value represents one of two choices: True or False. It’s like answering a yes/no question.
What is 'None' in Python? None' in Python is like having an empty box. It represents the absence of a value or a null value in variables
What are strings and how do I work with them? Strings are sequences of characters, like words or sentences. You can create them by enclosing characters in quotes. Python lets you add strings together, find their length, and extract parts of them using indexing.
What are data types in Python? Data types in Python are like different kinds of containers; each type—like integers, floats, and strings—holds data in a unique way, suitable for various needs
What is a dictionary in Python? A dictionary in Python is like a real dictionary; it stores words (keys) and their meanings (values) in a way that you can quickly look them up
How do I add an item to a dictionary in Python? Adding an item to a dictionary is like adding a new entry in your phone’s contact list. You define a key and its value: my_dict['new_key'] = 'new_value'.
What happens if I try to access a key that doesn't exist in the dictionary? Trying to access a key that doesn't exist in a dictionary is like trying to call a phone number you don’t have. Python will give you an error, but you can handle this smoothly with my_dict.get('unknown_key', 'default_value')
Can a dictionary key be a type other than a string? Yes, dictionary keys can be other types, like numbers or tuples, as long as they are 'immutable' (can’t be changed), much like using both names and numbers as identifiers in a filing system.
How do I merge two dictionaries together? Merging two dictionaries is like combining two decks of cards. You can use the update() method: dict1.update(dict2) will add items from dict2 to dict1, with dict2's items overriding any duplicates.
How can I loop over a dictionary? Looping over a dictionary is like checking every drawer in a cabinet. You can loop through keys, values, or both together using methods like .keys(), .values(), or .items().
What is a good use case for dictionaries in programming? Dictionaries are great for scenarios where quick lookup, addition, or deletion of data based on unique keys is needed, such as storing user information or settings in an application.
How do I find the number of items in a dictionary? Finding the number of items in a dictionary is like counting the number of contacts in your phone. You can find it using len(my_dict)
Can I have a dictionary within another dictionary? Yes, you can have dictionaries within dictionaries, which is like having folders within folders on a computer. This can be useful for representing hierarchical data
How do I copy a dictionary properly? Copying a dictionary properly to avoid altering the original by mistake can be done with my_dict.copy() for a shallow copy or copy.deepcopy(my_dict) from the copy module for a deep copy, ensuring that all nested dictionaries are also copied independently.
What does 'syntax error' mean? A syntax error occurs when the Python language rules aren't followed, similar to making grammatical mistakes in English.
What is an exception in Python? An exception is like receiving an unexpected problem while following a recipe. It’s something that disrupts the normal flow of the program, and you can plan to handle these disruptions
How do you use the assert statement, and what is its purpose? The assert statement in Python is like a checkpoint that tests whether a condition is true. It helps catch bugs by stopping the program if the condition is false.
What is a function in Python? A function is like a recipe that tells you how to achieve a specific task. You give it ingredients (inputs), and it gives you back a result (output)
What is 'pass' used for in Python? The 'pass' statement is like saying "do nothing here." It acts as a placeholder in areas of your code where Python expects an expression
What is the purpose of a function in programming? A function in programming is like a machine in a factory; you put something in (inputs), it does a job, and then it gives something back (outputs). Functions help you reuse code without rewriting it
What is the difference between a function that returns a value and one that doesn’t? A function that returns a value sends out a product, like a vending machine delivering a snack. A function that doesn’t return a value might still do work, like turning on lights, but doesn’t give anything back.
What is the difference between passing by value and passing by reference? Pass by value is like sending a copy of a document to someone; changes made don't affect the original. Pass by reference is like giving someone your original document; changes they make also appear on your copy
How can default parameters be used in functions? Default parameters are like backup singers in a band; if the main singer (the caller of the function) doesn’t provide enough voices (arguments), the backup singers (default parameters) fill in automatically
How does function scope work in Python? Function scope in Python is like having a conversation in a closed room. Variables created inside the function (spoken words inside the room) are not heard (accessible) outside the function unless explicitly passed out.
What are lists in Python? Lists in Python are like rows in a grocery list. They keep items in a particular order, and you can add, remove, or find items as needed.
How do you find the length of a list in Python? Finding the length of a list in Python is like counting how many people are in a line. You use the len() function, which tells you how many items are in the list.
What does slicing a list do? Slicing a list is like cutting a piece of cake; you take a section of the list. For example, my_list[1:4] gets you a new list with items from position 1 to 3, not including position 4.
What happens when you multiply a list by a number? Multiplying a list by a number, say 3, is like photocopying a flyer three times. It repeats the list items that many times. For instance, [1, 2, 3] * 3 results in [1, 2, 3, 1, 2, 3, 1, 2, 3]
How do you check if an item is in a list? Checking if an item is in a list is like looking for a friend in a crowd. You can use the in keyword. If name in my_list is True, your friend is in the crowd!
What does appending an item to a list do? Appending an item to a list is like adding a new car to the end of a train. You use my_list.append(item) to add the item to the end of my_list.
How do you combine two lists? Combining two lists is like merging two lines into one. You can add them together with +, like list_one + list_two, or use list_one.extend(list_two) to add all items from list_two into list_one
What does 'loop' mean in programming? A loop in programming is similar to running laps around a track. You keep going around the track until you've completed the laps. In programming, you keep repeating actions until a certain condition is met
What is a nested loop, and where could it be useful? A nested loop is like having a smaller clockwork inside a larger one, where each tick of the outer loop triggers a full cycle of the inner loop. It's useful for tasks that require repeated actions within repeated actions, such as checking every cell in a grid.
How do while loops operate? A while loop in Python keeps running like a clock, as long as its condition remains true, perfect for when you don’t know how many times you’ll need to loop.
What do for and while loops do in Python? for loops and while loops in Python are like repeating a set of instructions until a task is done. for loops repeat for a specific number of times, and while loops continue as long as a condition is true.