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"""
This module provides functionality for caching and looking up fully qualified function
and class names from Python source files by line number.
It uses Python's tokenize module to parse source files and tracks function/class
definitions along with their nesting to build fully qualified names (e.g. 'class.method'
or 'module.function'). The results are cached in a two-level dictionary mapping:
filename -> (line_number -> fully_qualified_name)
Example usage:
name = get_funcname("myfile.py", 42) # Returns name of function/class at line 42
clearcache() # Clear the cache if file contents have changed
The parsing is done lazily when a file is first accessed. Invalid Python files or
IO errors are handled gracefully by returning empty cache entries.
"""
import tokenize
from typing import Optional
cache: dict[str, dict[int, str]] = {}
def clearcache() -> None:
cache.clear()
def _add_file(filename: str) -> None:
try:
with tokenize.open(filename) as f:
tokens = list(tokenize.generate_tokens(f.readline))
except (OSError, tokenize.TokenError):
cache[filename] = {}
return
# NOTE: undefined behavior if file is not valid Python source,
# since tokenize will have undefined behavior.
result: dict[int, str] = {}
# current full funcname, e.g. xxx.yyy.zzz
cur_name = ""
cur_indent = 0
significant_indents: list[int] = []
for i, token in enumerate(tokens):
if token.type == tokenize.INDENT:
cur_indent += 1
elif token.type == tokenize.DEDENT:
cur_indent -= 1
# possible end of function or class
if significant_indents and cur_indent == significant_indents[-1]:
significant_indents.pop()
# pop the last name
cur_name = cur_name.rpartition(".")[0]
elif (
token.type == tokenize.NAME
and i + 1 < len(tokens)
and tokens[i + 1].type == tokenize.NAME
and (token.string == "class" or token.string == "def")
):
# name of class/function always follows class/def token
significant_indents.append(cur_indent)
if cur_name:
cur_name += "."
cur_name += tokens[i + 1].string
result[token.start[0]] = cur_name
cache[filename] = result
def get_funcname(filename: str, lineno: int) -> Optional[str]:
if filename not in cache:
_add_file(filename)
return cache[filename].get(lineno, None)
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