跟踪Python嵌套函数调用 Aug 27th, 2012 今天在浏览Google Reader的时候发现一个好用的工具函数，用来跟踪嵌套调用函数方便debug。 原文：Easy tracing of nested function calls in Python 其实是一个装饰器类： import sys from functools import wraps class TraceCalls(object): """ Use as a decorator on functions that should be traced. Several functions can be decorated - they will all be indented according to their call depth. """ def __init__(self, stream=sys.stdout, indent_step=2, show_ret=False): self.stream = stream self.indent_step = indent_step self.show_ret = show_ret # This is a class attribute since we want to share the indentation # level between different traced functions, in case they call # each other. TraceCalls.cur_indent = 0 def __call__(self, fn): @wraps(fn) def wrapper(*args, **kwargs): indent = ' ' * TraceCalls.cur_indent argstr = ', '.join( [repr(a) for a in args] + ["%s=%s" % (a, repr(b)) for a, b in kwargs.items()]) self.stream.write('%s%s(%s)\n' % (indent, fn.__name__, argstr)) TraceCalls.cur_indent += self.indent_step ret = fn(*args, **kwargs) TraceCalls.cur_indent -= self.indent_step if self.show_ret: self.stream.write('%s--> %s\n' % (indent, ret)) return ret return wrapper #=================== Test Case 1 @TraceCalls() def iseven(n): return True if n == 0 else isodd(n - 1) @TraceCalls() def isodd(n): return False if n == 0 else iseven(n - 1) print(iseven(7)) """ Output: iseven(7) isodd(6) iseven(5) isodd(4) iseven(3) isodd(2) iseven(1) isodd(0) False """ #=================== Test Case 2 @TraceCalls(indent_step=4, show_ret=True) def flatten(lst): if isinstance(lst, list): return sum((flatten(item) for item in lst), []) else: return [lst] list(flatten([1, 2, [3, [4, 5], 6, [7, [9], 12]], 4, [6, 9]])) """ flatten([1, 2, [3, [4, 5], 6, [7, [9], 12]], 4, [6, 9]]) flatten(1) --> [1] flatten(2) --> [2] flatten([3, [4, 5], 6, [7, [9], 12]]) flatten(3) --> [3] flatten([4, 5]) flatten(4) --> [4] flatten(5) --> [5] --> [4, 5] flatten(6) --> [6] flatten([7, [9], 12]) flatten(7) --> [7] flatten([9]) flatten(9) --> [9] --> [9] flatten(12) --> [12] --> [7, 9, 12] --> [3, 4, 5, 6, 7, 9, 12] flatten(4) --> [4] flatten([6, 9]) flatten(6) --> [6] flatten(9) --> [9] --> [6, 9] --> [1, 2, 3, 4, 5, 6, 7, 9, 12, 4, 6, 9] """