Is there a way to check whether function output is assigned to a variable in Python?

Question

In Python, I\'d like to write a function that would pretty-print its results to the console if called by itself (mostly for use interactively or for debugging). For the purpose

Answer 1

New Solution

This is a new that solution detects when the result of the function is used for assignment by examining its own bytecode. There is no bytecode writing done, and it should even be compatible with future versions of Python because it uses the opcode module for definitions.

import inspect, dis, opcode

def check_status():

    try:
        frame = inspect.currentframe().f_back
        next_opcode = opcode.opname[ord(frame.f_code.co_code[frame.f_lasti+3])]
        if next_opcode == "POP_TOP": 
            # or next_opcode == "RETURN_VALUE":
            # include the above line in the if statement if you consider "return check_status()" to be assignment
            print "I was not assigned"
            print "Pretty printer status check 0.02v"
            print "NOTE: This is so totally not written for giant robots"
            return
    finally:
        del frame    

    # do normal routine

    info = {'cond_op': 1, 't_canoncharge': 1342, 'stage_booster': 5}

    return info

# no assignment    
def test1():
    check_status()

# assignment
def test2():
    a = check_status()

# could be assignment (check above for options)
def test3():
    return check_status()

# assignment
def test4():
    a = []
    a.append(check_status())
    return a

Solution 1

This is the old solution that detects whenever you are calling the function while debugging under python -i or PDB.

import inspect

def check_status():
    frame = inspect.currentframe()
    try:
        if frame.f_back.f_code.co_name == "" and frame.f_back.f_code.co_filename == "":
            print "Pretty printer status check 0.02v"
            print "NOTE: This is so totally not written for giant robots"
    finally:
        del frame

    # do regular stuff   
    return {'cond_op': 1, 't_canoncharge': 1342, 'stage_booster': 5}

def test():
    check_status()


>>> check_status()
Pretty printer status check 0.02v
NOTE: This is so totally not written for giant robots
{'cond_op': 1, 't_canoncharge': 1342, 'stage_booster': 5}

>>> a=check_status()
Pretty printer status check 0.02v
NOTE: This is so totally not written for giant robots

>>> a
{'cond_op': 1, 't_canoncharge': 1342, 'stage_booster': 5}

test()
>>>