Trace functions that are called on Python strings

问题

Is it possible in Python to trace and filter functions that are called on strings during program run? I want to add sys.setdefaultencoding("utf-8") application, and I want to set some guards to predict potential problems with misusing standard functions (like len, for example), to process such strings.

回答1:

You can replace the builtin:

import __builtin__

real_len = __builtin__.len

def checked_len(s):
    ... do extra checks ...
    return real_len(s)

__builtin__.len = checked_len

来源：https://stackoverflow.com/questions/29586776/trace-functions-that-are-called-on-python-strings