34 lines
999 B
Markdown
34 lines
999 B
Markdown
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---
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categories:
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- Programming Languages
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tags: [python]
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---
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# Lambdas in Python
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In Python, anonymous functions like arrow-functions in JavaScript (`() => {}`) are immediately invoked and unnamed. They are called lambdas.
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Whilst they are unnamed, just like JS, the value they return can be stored in a variable. They do not require the `return` keyword.
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They are most often used unnamed with the functional methods [map, filter and reduce](/Programming_Languages/Python/Syntax/Map_filter_reduce_in_Python.md)
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Here is the two syntaxes side by side:
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```js
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const double = (x) => x * x;
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```
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```py
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double = lambda x: x * x
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```
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Here is a lambda with multiple parameters:
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```py
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func = lambda x, y, z: x + y + z
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print(func(2, 3, 4))
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# 9
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```
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> Lambdas obviously enshrine functional programming paradigms. Therefore they should be pure functions, not mutating values or issueing side effects. For example, it would be improper (though syntactically well-formed) to use a lambda to `print` something
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