Python小姿势 - 5 tips to get the most out of list comprehensions in Python

5 tips to get the most out of list comprehensions in Python

Python's list comprehensions are a beautiful way to simplify your code and make it more readable. But they can also be a little daunting at first glance. In this article, I'll share 5 tips to help you get the most out of list comprehensions in Python.

Tip 1: Use list comprehensions to create lists

This may seem like a no-brainer, but it's worth mentioning. List comprehensions are a great way to create lists. For example, let's say you want to create a list of the first 10 square numbers. You could do it like this:

squares = [i**2 for i in range(10)]

squares

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

As you can see, this is much simpler than using a for loop to construct the list.

Tip 2: Use list comprehensions to transform lists

In addition to creating lists, list comprehensions can also be used to transform lists. For example, let's say you have a list of strings, and you want to convert them all to uppercase. You could do it like this:

strings = ['foo', 'bar', 'baz']

uppercase_strings = [s.upper() for s in strings]

uppercase_strings

['FOO', 'BAR', 'BAZ']

Again, this is much simpler than using a for loop.

Tip 3: Use list comprehensions to filter lists

List comprehensions can also be used to filter lists. For example, let's say you have a list of integers, and you want to get only the even numbers. You could do it like this:

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

even_numbers = [n for n in numbers if n % 2 == 0]

even_numbers

[2, 4, 6, 8, 10]

As you can see, this is much simpler than using a for loop and an if statement.

Tip 4: Use list comprehensions with multiple for loops

List comprehensions can also be used with multiple for loops. For example, let's say you want to create a list of all the possible combinations of two lists. You could do it like this:

list1 = [1, 2, 3]

list2 = ['a', 'b', 'c']

combinations = [(x, y) for x in list1 for y in list2]

combinations

[(1, 'a'), (1, 'b'), (1, 'c'), (2, 'a'), (2, 'b'), (2, 'c'), (3, 'a'), (3, 'b'), (3, 'c')]

As you can see, this is much simpler than using nested for loops.

Tip 5: Use list comprehensions with conditionals

List comprehensions can also be used with conditionals. For example, let's say you want to create a list of all the possible combinations of two lists, but you only want the combinations that contain the number 2. You could do it like this:

list1 = [1, 2, 3]

list2 = ['a', 'b', 'c']

combinations = [(x, y) for x in list1 for y in list2 if x == 2]

combinations

[(2, 'a'), (2, 'b'), (2, 'c')]

As you can see, this is much simpler than using a for loop and an if statement.

I hope these tips will help you get the most out of list comprehensions in Python.