Python Decorator用于打印函数执行的每一行 [英] Python Decorator for printing every line executed by a function

问题描述

出于调试目的，我想打印出与python方法中执行的每一行有关的内容。

I want to, for debugging purposes, print out something pertaining to each and every line executed in a python method.

例如，如果该行中有一些赋值，我想打印为该变量分配的值，如果有函数调用，我想打印出由函数等返回的值。

For example if there was some assignment in the line, i want to print what value was assigned for that variable, and if there was a function call, i want to print out the value returned by the function, etc.

因此，例如，如果我要使用装饰器，则将其应用于函数/方法，例如：

So, for example if i were to use a decorator, applied on function/method such as :

@some_decorator
def testing() : 
    a = 10
    b = 20
    c = a + b
    e = test_function()

调用函数测试时，应打印以下内容：

the function testing when called, should print the following :

a = 10
b = 20  
c = 30
e = some_value

有没有办法实现这一目标？更重要的是，我想知道我是否可以编写可以逐行通过其他代码的代码，检查它是哪种类型的指令，等等。或者也许像我们可以找到一个字典来找出其中的所有变量一个类，我能否得到像数据结构这样的字典来获取函数中的每条指令，这是元程序所能获得的。

Is there some way to achieve this? More fundamentally, i want to know whether i can write a code that can go through some other code line by line, check what type of an instruction it is, etc. Or maybe like we can get a dictionary for finding out all the variables in a class, can i get a dictionary like datastructure for getting every instruction in a function, which is as good a metaprogram can get.

因此，我特别想找一个解决方案使用装饰器，我很好奇是否可以有一个装饰器可以逐行遍历整个功能，并逐行装饰它，
但欢迎任何解决方案。

Hence, I am particularly looking a solution using decorators, as I am curious if one can have a decorator that can go through an entire function line by line, and decorate it line by line, but any and all solutions are welcome.

预先感谢。

推荐答案

这样的事情怎么样？

调试上下文：

import sys

class debug_context():
    """ Debug context to trace any function calls inside the context """

    def __init__(self, name):
        self.name = name

    def __enter__(self):
        print('Entering Debug Decorated func')
        # Set the trace function to the trace_calls function
        # So all events are now traced
        sys.settrace(self.trace_calls)

    def __exit__(self, *args, **kwargs):
        # Stop tracing all events
        sys.settrace = None

    def trace_calls(self, frame, event, arg): 
        # We want to only trace our call to the decorated function
        if event != 'call':
            return
        elif frame.f_code.co_name != self.name:
            return
        # return the trace function to use when you go into that 
        # function call
        return self.trace_lines

    def trace_lines(self, frame, event, arg):
        # If you want to print local variables each line
        # keep the check for the event 'line'
        # If you want to print local variables only on return
        # check only for the 'return' event
        if event not in ['line', 'return']:
            return
        co = frame.f_code
        func_name = co.co_name
        line_no = frame.f_lineno
        filename = co.co_filename
        local_vars = frame.f_locals
        print ('  {0} {1} {2} locals: {3}'.format(func_name, 
                                                  event,
                                                  line_no, 
                                                  local_vars))

调试装饰器：

def debug_decorator(func):
    """ Debug decorator to call the function within the debug context """
    def decorated_func(*args, **kwargs):
        with debug_context(func.__name__):
            return_value = func(*args, **kwargs)
        return return_value
    return decorated_func

用法

@debug_decorator
def testing() : 
    a = 10
    b = 20
    c = a + b

testing()

输出

###########################################################
#output:
#   Entering Debug Decorated func
#     testing line 44 locals: {}
#     testing line 45 locals: {'a': 10}
#     testing line 46 locals: {'a': 10, 'b': 20}
#     testing return 46 locals: {'a': 10, 'b': 20, 'c': 30}
###########################################################

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