PyFence: type verification for Python

PyFence is a self-made utility-library that allows you to monitor type matching while debugging your project. PyFence takes type information from function docstrings in the standard Sphinx format . That is, if you already have documentation, you do not need to do anything else to use PyFence!

For example, take the following class:

classRationalFormatter(object):defformat(self, number):"""
        Stringifies a number to numerator/denominator format
        Example::
            >>> print(RationalFormatter().format(1.25))
            5/4
        :param number: input number
        :type  number: float
        :raises      : None
        :rtype       : str
        """return'%i/%i' % number.as_integer_ratio()
    defdisplay(self, number):
        print(str(number) + ' = ' + self.format(number))

The format method represents a fraction number using the float.as_integer_ratio ()
method .
Try:

>>> from formatter import RationalFormatter
>>> f = RationalFormatter()
>>> f.display(1.25)
1.25 = 5/4

Does it seem to work? However, everything will break if you pass int , because int , unfortunately, does not contain .as_integer_ratio () .

>>> f.display(5)
Traceback (most recent call last):
  File "example.py", line 5, in <module>
    f.display(5)
  File "/home/eugeny/Work/pyfence/example_formatter.py", line 18, in display
    print(str(number) + ' = ' + self.format(number))
  File "/home/eugeny/Work/pyfence/example_formatter.py", line 15, in format
    return'%i/%i' % number.as_integer_ratio()
AttributeError: 'int' object has no attribute 'as_integer_ratio'

However, when using PyFence, such a problem could have been noticed much earlier:

$ pip install pyfence
...
$ fence example.py --fence:strict,stop
1.25 = 5/4
 *** PyFence ERROR ---------------------------
 *** PyFence ERROR PyFence verification failed
 *** PyFence ERROR  :: example_formatter.RationalFormatter.format(<example_formatter.RationalFormatter object at 0x7ff097a47d10>, 5)
 *** PyFence ERROR in example_formatter.py:2
 *** PyFence ERROR number was 5 (int) instead of ['float']
 *** PyFence ERROR Aborting

In addition, PyFence can check the types of exceptions and return types that occur in functions / methods.
You can also import the pyfence module in the project itself, in which case you do not have to use a separate fence utility .
Of course, it is worth using fence only during development, and not in production, since due to checks, a drop in performance is possible.

I will be very grateful to any feedback and pull requests !