Trace python function calls, arguments and return values

trace.py

from functools import wraps
indent = 0
def trace(func):
    @wraps(func)
    def function_wrapper(*args, **kwargs):
        """function_wrapper of trace"""
        global indent
        print("{indent} HI {func_name}, args={args}, kargs={kwargs}".format(indent="\t"*indent, func_name=func.__name__, args=args, kwargs=kwargs))
        indent += 1
        res = func(*args, **kwargs)
        indent -= 1
        print("{indent} Bye {func_name}, return={ret_val}".format(indent="\t"*indent, func_name=func.__name__, ret_val=res))
        return res
    return function_wrapper

if __name__ == "__main__":
    # Demo
    @trace
    def a(*args, **kwargs):
        return "a_out"

    @trace
    def b(*args, **kwargs):
        c("c1", "c2")
        return "b_out"

    @trace
    def c(*args, **kwargs):
        return "c_out"

    @trace
    def d(*args, **kwargs):
        return "d_out"

    @trace
    def main():
        a("a1", "a2")
        b("b1", "b2")
        d("d1", "d2")
    
    main()

    # Output: python trace.py
    """
 HI main, args=(), kargs={}
         HI a, args=('a1', 'a2'), kargs={}
         Bye a, return=a_out
         HI b, args=('b1', 'b2'), kargs={}
                 HI c, args=('c1', 'c2'), kargs={}
                 Bye c, return=c_out
         Bye b, return=b_out
         HI d, args=('d1', 'd2'), kargs={}
         Bye d, return=d_out
 Bye main, return=None
    """