# List Comprehensions

List Comprehensions: In addition to sequence operations and list methods, Python includes a more advanced operation called a list comprehension.

List comprehensions allow us to build out lists using a different notation. You can think of it as essentially a one line `for`

loop built inside of brackets. For a simple example:

## Example 1

```
# Grab every letter in string
lst = [x for x in 'word']
```

```
# Check
lst
```

This is the basic idea of a list comprehension. If you’re familiar with mathematical notation this format should feel familiar for example: x^2 : x in { 0,1,2…10 }

Let’s see a few more examples of list comprehensions in Python:

## Example 2

```
# Square numbers in range and turn into list
lst = [x**2 for x in range(0,11)]
```

```
lst
```

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## Example 3

Let’s see how to add in `if`

statements:

```
# Check for even numbers in a range
lst = [x for x in range(11) if x % 2 == 0]
```

```
lst
```

## Example 4

Can also do more complicated arithmetic:

```
# Convert Celsius to Fahrenheit
celsius = [0,10,20.1,34.5]
fahrenheit = [((9/5)*temp + 32) for temp in celsius ]
fahrenheit
```

## Example 5

We can also perform nested list comprehensions, for example:

```
lst = [ x**2 for x in [x**2 for x in range(11)]]
lst
```

```
for x in range(11):
for x in [x ** 2]:
lst = []
lst.append(x ** 2)
lst
```

Later on in the course we will learn about generator comprehensions. After this lecture you should feel comfortable reading and writing basic list comprehensions.

Also Read: WHILE LOOPS