if_

Optional chaining for Python

Installation

python setup.py install

Usage

Call if_() with a Python expression, and chain attribute and item accessors on the return value, ending with ._. If the initial expression evaluates to None, so will the whole chain; if not, each accessor will run normally but if it fails the chain will return None.

In a boolean or equality test you can leave off the ._.

Examples

In [1]: from if_ import if_

In [2]: d = {
   ...:     'a': 123,
   ...:     'c': None,
   ...:     'd': {'this': 456},
   ...:     'l': [1, 2, 3],
   ...:     'f': lambda x: x * 11,
   ...: }

In [3]: if_(None).anything._ is None
Out[3]: True

In [4]: if_(d).anything._ is None
Out[4]: True

In [5]: if_(d)['a']._ == 123
Out[5]: True

In [6]: if_(d)['c']['anything']._ is None
Out[6]: True

In [7]: if_(d)['l'][1]._ == 2
Out[7]: True

In [8]: if_(d)['l'][5]._ is None
Out[8]: True

In [9]: if_(d)['f'](4) == 44
Out[9]: True