Including the current method name when printing in Python

Question

Often times in C programs (and using GCC) I will create a debug print macro that includes the name of the current function. That is, something like:

#define DPRINTF(fmt, ...) printf("[%s] " fmt, __FUNCTION__, ##__VA_ARGS__)

When used, the current function will be prepended to each print, providing more useful debug information at runtime. For example, the following code

#include <stdio.h>

#define DPRINT(fmt, ...) printf("[%s] " fmt, __FUNCTION__, ##__VA_ARGS__)

void testfunction1(){
    DPRINT("Running %d\n",1);
}

void testfunction2(){
    DPRINT("Running %d\n",2);
}

int main(void) {
    DPRINT("Running: %d\n",0);
    testfunction1();
    testfunction2();
    return 0;
}

Would output:

[main] Running: 0
[testfunction1] Running 1
[testfunction2] Running 2

Can something like this be done in Python?

I searched around a bit and found this StackOverflow question explaining how inspect can be used to read names from the stack. However, from what I've found Python does not support macros, so the same form as my C program cannot be used.

Is there some mechanism by which this type of debug printing can be supported? I tried lambdas, but the "function name" in this case prints as "< lambda >".

can you put the sample code of what you tried?, it is often easy to start from there. To quickly answer, yes you could , check the use of decorators in python. you could wrap a function to debug its name. — suvy, Jun 13 '17 at 13:59

score 4 · Answer 1 · answered Jun 13 '17 at 13:53

You can inspect the last frame to retrieve the caller name and the rest is simple formatting, something like

import sys

def dprint(fmt=None, *args, **kwargs):
    try:
        name = sys._getframe(1).f_code.co_name
    except (IndexError, TypeError, AttributeError):  # something went wrong
        name = "<unknown>"
    print("[{}] {}".format(name, (fmt or "{}").format(*args, **kwargs)))

def testfunction1():
    dprint("Running {}", 1)

def testfunction2():
    dprint("Running {}", 2)

def main():
    dprint("Running {}", 0)
    testfunction1()
    testfunction2()
    return 0

if __name__ == "__main__":
    main()

# prints:
# [main] Running 0
# [testfunction1] Running 1
# [testfunction2] Running 2

score 4 · Answer 2 · answered Jun 13 '17 at 14:09

I would suggest not using print at all, and instead setup a logger. The logging module has a funcName attribute available for all LogRecords.

You'll then have (code taken from zwer's answer):

import logging

def create_logger(app_name=None):
    logger = logging.getLogger(app_name or __name__)
    logger.setLevel(logging.DEBUG)
    log_format = '[%(asctime)-15s] [%(levelname)08s] (%(funcName)s %(message)s'
    logging.basicConfig(format=log_format)
    return logger

LOGGER = create_logger()

def testfunction1():
    LOGGER.info("Running %d", 1)

def testfunction2():
    LOGGER.error("Running %s", 2)

def main():
    LOGGER.debug("Running %03d", 0)
    testfunction1()
    testfunction2()

if __name__ == "__main__":
    main()

which will generate something similar to:

[2017-06-13 19:41:45,677] [   DEBUG] (main) Running 000
[2017-06-13 19:41:45,677] [    INFO] (testfunction1) Running 1
[2017-06-13 19:41:45,677] [   ERROR] (testfunction2) Running 2

a much more robust answer – Amey Kumar Samala Jun 13 '17 at 14:17 — Amey Kumar Samala, Jun 13 '17 at 14:17

Amey Kumar Samala · Answer 3 · 2017-06-13T14:16:59.047

1

import inspect
import sys
def DPRINT(fmt, *args):
    print "{} {} {}".format(sys._getframe(1).f_code.co_name, fmt, args)

    # below line is another way to get the name of a calling function
    # print "{} {} {}".format(inspect.stack()[1][3], fmt, args)

def testfunction1():
    DPRINT("Running: 1")

def testfunction2():
    DPRINT("Running: 2")

def main():
    DPRINT("Running: 0")
    testfunction1()
    testfunction2()

main()

I don't know if this could be helpful

edited Jun 13 '17 at 14:16

answered Jun 13 '17 at 13:52

Amey Kumar Samala

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Oh .. man. As I was reading your solution it was so obvious. If you can read the current function's name from the stack then you could also just read the caller's name from the stack .. – sherrellbc Jun 13 '17 at 13:53
True indeed @sherrellbc – Amey Kumar Samala Jun 13 '17 at 13:54
1

@AmeyYadav - reading the whole stack just to grab the last frame is awfully wasteful, tho. – zwer Jun 13 '17 at 13:55
@zwer for obvious reasons I wasn't thinking of an optimized answer, I just new one way to do it, there could be a million more. – Amey Kumar Samala Jun 13 '17 at 14:12

Including the current method name when printing in Python

3 Answers3