45 lines
978 B
Markdown
45 lines
978 B
Markdown
---
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tags:
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- python
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- aws-lambda
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- AWS
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---
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# Lambdas in Python
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In Python, anonymous functions like arrow-functions in JavaScript (`() => {}`)
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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
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variable. They do not require the `return` keyword.
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They are most often used unnamed with the functional methods
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[map, filter](Map_and_filter_in_Python.md)
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and reduce.
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Here is the two syntaxes side by side:
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```js
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// JavaScript
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const double = (x) => x * x;
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```
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```py
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# Python
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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
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> should be pure functions, not mutating values or issueing side effects. For
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> example, it would be improper (though syntactically well-formed) to use a
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> lambda to `print` something
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