Write short and fully-typed lambdas where you need them.

• Allows to write lambdas as _
• Fully typed with annotations and checked with mypy, PEP561 compatible
• Has a bunch of helpers for better composition
• Easy to start: has lots of docs, tests, and tutorials

pip install lambdas

You also need to configure mypy correctly and install our plugin:

# In setup.cfg or mypy.ini: [mypy] plugins = lambdas.contrib.mypy.lambdas_plugin

We recommend to use the same mypy settings we use.

Imagine that you need to sort an array of dictionaries like so:

>>> scores = [ ... {'name': 'Nikita', 'score': 2}, ... {'name': 'Oleg', 'score': 1}, ... {'name': 'Pavel', 'score': 4}, ... ] >>> print(sorted(scores, key=lambda item: item['score'])) [{'name': 'Oleg', 'score': 1}, {'name': 'Nikita', 'score': 2}, {'name': 'Pavel', 'score': 4}]

And it works perfectly fine. Except, that you have to do a lot of typing for such a simple operation.

That's where lambdas helper steps in:

>>> from lambdas import _ >>> scores = [ ... {'name': 'Nikita', 'score': 2}, ... {'name': 'Oleg', 'score': 1}, ... {'name': 'Pavel', 'score': 4}, ... ] >>> print(sorted(scores, key=_['score'])) [{'name': 'Oleg', 'score': 1}, {'name': 'Nikita', 'score': 2}, {'name': 'Pavel', 'score': 4}]

It might really save you a lot of effort, when you use a lot of lambda functions. Like when using returns library.

We can easily create math expressions:

>>> from lambdas import _ >>> math_expression = _ * 2 + 1 >>> print(math_expression(10)) 21 >>> complex_math_expression = 50 / (_ ** 2) * 2 >>> print(complex_math_expression(5)) 100.0

Work in progress:

• _.method() is not supported yet for the same reason
• TypedDicts are not tested with __getitem__
• __getitem__ does not work with list and tuples (collections), only dicts (mappings)

For now you will have to use regular lamdbas in these cases.