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This is a Python 3.6 module to profile function performance. It records the number of calls made to select functions, and outputs statistics about their execution times.


There are two ways to install this package from the terminal:

Directly from PyPI (recommended):

pip3 install function-profiler

From source:

  1. git clone
  2. cd Function-Profiler
  3. sudo python3 install

In either of these ways, it may be acceptable to use pip or python instead of pip3 and python3 respectively, depending on your local configuration.

Explanation, Basic Use

The profiler has three components:

  • function_profiler, a decorator for functions to have their calls logged
  • FunctionLogger, a class that acts as a context manager for the decorated functions, and which stores (as class variables) the number of calls to each decorated function, as well as their execution time lengths. It also has a class method, FunctionLogger.log_data, which outputs the logged call/time data (to stderr by default).
  • with_logger, a decorator that calls profiler.FunctionLogger.log_data after the function it wraps has exited (whether by normal return or by exception). This is useful if, for example, you want to output logs just once, after your main function has exited. (Or if you want to output logs every time some particular function exits, etc.)


import profiler

def foo():




foo: 3 calls. Time stats (seconds): Min: 0.000001, Mean: 0.000002, Median: 0.000002, Max: 0.000003, Stddev: 0.000001


Suppose we have a file,

import profiler

def foo():

def main():

if __name__=='__main__':

and we run this from the command line, i.e. python3 We get this output at the command-line:

foo: 1 call. Time stats (seconds): Min: 0.000001, Mean: 0.000002, Median: 0.000002, Max: 0.000003, Stddev: 0.000001


profiler.FunctionLogger.log_data takes one of three options:

  • 'stdout' if you wish the output to be logged to stdout
  • 'stderr' if you wish the output to be logged to stderr
  • 'suppress' if you wish the output not to be logged
  • any other string, e.g. 'myfile.txt' will cause the output to be logged to a file of that name.

Since with_logger calls profiler.FunctionLogger.log_data, with_logger also accepts the same set of three options.

If you don't want the summary statistics but rather more granular ones, you can access profiler.FunctionLogger's class variables directly. There are two:

  • profiler.FunctionLogger.call_frequencies is a dict mapping each function to the number of times it has been called.
  • profiler.FunctionLogger.call_times is a dict mapping each function to a list of how long it took to complete each function call.

Finally, profiler.function_profiler accepts one argument: a naming convention, either 'qualname' (default) or 'name'. This is because profiler.FunctionLogger stores data on functions by using their names as keys. By default, it uses the functions' fully qualified names in order to prevent name collisions, but by supplying 'name' instead, it'll just use the function's local name.

Tests and Examples

It is possible to run tests for profiler before installing the module.

From the top-level directory, simply run python3 (In order to run the tests without installing the package, the tests use os.getcwd() and then try to locate the profiler module using its relative path, which assumes that the tests are being run from the top-level directory.)

Examples are located in the examples/ directory, and should similarly be run from the top-level directory, e.g. python3 examples/ If you're uncertain about using this library, then hopefully the examples will be useful references.

Common Errors

Note that profiler.FunctionLogger acts as a context manager on a function call. Consequently, a function that does not exit will not have its call time logged. Common cases in which you might face this error include interrupting the program before a function call finishes, or writing a function that exceeds the maximum recursion depth (so functions are repeatedly entered, but never exited before erring).


This package is intended for Python 3. It doesn't currently work for Python 2, though it should be easy to achieve that compatibility if you need it. I am firmly moving on to Python 3.6+, consequently I will not be writing any code to ensure backwards compatibility. However, I am willing to bless Python 2.7-compatible forks, should they appear.


This package lives here on PyPI.

There's also an entry about this project on my blog.


Python 3.6 Module to Profile Function Performance in Production








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