How to differentiate between “a string” and “a actual code” in python?

Question

My works relates to instrumentation of code fragments in python code. So in my work i would be writing a script in python such that I take another python file as input and i

Answer 1

You could use a Regular Expression. To avoid def inside quotes then you can use negative look-arounds:

import re

for line in open('A.py'):
    m = re.search(r"(?!<[\"'])\bdef\b(?![\"'])", line)
    if m:
        print r'@decorator    #<------ inserted code' 

    print line 

However, there might be other occurances of def that you or I can't think of, and if we are not careful we end-up writing the Python parser all over again. @Janne Karila's suggestion of using ast.parse is probably safer in the long term.

Answer 2

Use the ast module to parse the file properly.

This code prints the line number and column offset of each def statement:

import ast
with open('mymodule.py') as f:
    tree = ast.parse(f.read())
for node in ast.walk(tree):
    if isinstance(node, ast.FunctionDef):
        print node.lineno, node.col_offset