Create lambda-functions.md

Author: jAniceto

python/lambda-functions.md

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+# Annonymous functions (Lambda functions)
+
+Sometimes, naming a function is not worth the trouble. For example when you’re sure the function will only be used once. For such cases, Python offers us anonymous functions, also called lambda functions.
+
+A lambda function can be assigned to a variable, creating a concise way of defining a function:
+
+```python
+add_one = lambda x: x + 1
+add_one(3)
+# 4
+```
+
+It gets more interesting when you need to use a function as an argument. In such cases, the function is often used only once. As you may know, `map` applies a function to all elements of an iterable object. We can use a lambda when calling map:
+
+```python
+numbers = [1, 2, 3, 4]
+times_two = map(lambda x: x * 2, numbers)
+list(times_two)
+# [2, 4, 6, 8]
+```
+
+In fact, this is a pattern that you’ll see often. When you need to apply a relatively simple operation on each element of an iterable object, using `map()` in combination with a lambda function is concise and efficient.