funlog

funlog is a tiny but useful package that offers a few Python decorators to log function calls, with good control over what gets logged and when.

It also times the function call and logs arguments briefly but clearly, abbreviating arguments like long strings or dataclasses.

It is fully customizable with optional decorator arguments. You can log only slow calls, only if a function modifies its first argument, or tally calls and log them later.

I'm publishing it standalone since I often like to drop this into projects. It's often even faster than quick print-debugging and it lets you do very lightweight profiling by getting when certain functions are taking a lot of time and tallies of function calls and runtimes per function after a program runs a while or at exit.

Minimal dependencies (only the tiny strif).

Installation

pip install funlog

Usage

Suppose you have a few functions:

import time
import logging
from funlog import log_calls, log_tallies, tally_calls

# Set up logging however you like.
logging.basicConfig(level=logging.DEBUG, format="%(levelname)s:%(message)s", force=True)


@log_calls()
def add(a, b):
    return a + b


@tally_calls()
def sleep(n):
    time.sleep(0.01 * n)


@tally_calls()
def fibonacci(n):
    if n <= 1:
        return n
    sleep(n)
    return fibonacci(n - 1) + fibonacci(n - 2)


@log_calls()
def long_range(n):
    time.sleep(0.01 * n)
    return " ".join(str(i) for i in range(int(n)))


# Now call the functions.
long_range(fibonacci(add(add(5, 5), 2)))

log_tallies()

Running that gives you:

INFO:≫ Call: __main__.add(5, 5)
INFO:≪ Call done: __main__.add() took 0.00ms: 10
INFO:≫ Call: __main__.add(10, 2)
INFO:≪ Call done: __main__.add() took 0.00ms: 12
INFO:⏱ __main__.sleep() took 125ms, now called 1 times, 125ms avg per call, total time 125ms
INFO:⏱ __main__.sleep() took 114ms, now called 2 times, 119ms avg per call, total time 239ms
INFO:⏱ __main__.sleep() took 95.03ms, now called 4 times, 109ms avg per call, total time 438ms
INFO:⏱ __main__.sleep() took 55.05ms, now called 8 times, 89.25ms avg per call, total time 714ms
INFO:⏱ __main__.fibonacci() took 0.00ms, now called 1 times, 0.00ms avg per call, total time 0.00ms
INFO:⏱ __main__.fibonacci() took 0.00ms, now called 2 times, 0.00ms avg per call, total time 0.00ms
INFO:⏱ __main__.fibonacci() took 25.22ms, now called 3 times, 8.41ms avg per call, total time 25.22ms
INFO:⏱ __main__.fibonacci() took 59.16ms, now called 5 times, 16.88ms avg per call, total time 84.38ms
INFO:⏱ __main__.fibonacci() took 128ms, now called 9 times, 26.41ms avg per call, total time 238ms
INFO:⏱ __main__.fibonacci() took 243ms, now called 15 times, 37.59ms avg per call, total time 564ms
INFO:⏱ __main__.sleep() took 33.76ms, now called 16 times, 60.92ms avg per call, total time 975ms
INFO:⏱ __main__.fibonacci() took 429ms, now called 25 times, 49.00ms avg per call, total time 1.23s
INFO:⏱ __main__.fibonacci() took 741ms, now called 41 times, 61.40ms avg per call, total time 2.52s
INFO:⏱ __main__.sleep() took 32.68ms, now called 32 times, 48.04ms avg per call, total time 1.54s
INFO:⏱ __main__.fibonacci() took 23.35ms, now called 75 times, 67.37ms avg per call, total time 5.05s
INFO:⏱ __main__.sleep() took 24.54ms, now called 64 times, 43.64ms avg per call, total time 2.79s
INFO:⏱ __main__.fibonacci() took 60.07ms, now called 129 times, 78.67ms avg per call, total time 10.15s
INFO:⏱ __main__.fibonacci() took 55.71ms, now called 223 times, 91.26ms avg per call, total time 20.35s
INFO:⏱ __main__.sleep() took 44.42ms, now called 128 times, 40.64ms avg per call, total time 5.20s
INFO:⏱ __main__.fibonacci() took 2.07s, now called 396 times, 107ms avg per call, total time 42.19s
INFO:≫ Call: __main__.long_range(144)
INFO:≪ Call done: __main__.long_range() took 1.45s: '0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 …' (465 chars)
INFO:⏱ Function tallies:
    __main__.fibonacci() was called 465 times, total time 59.73s, avg per call 128ms
    __main__.sleep() was called 232 times, total time 9.11s, avg per call 39.25ms

There are several other options. See docstrings and test_examples.py for more docs and examples on all the options.

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This project was built from simple-modern-uv.