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:
# 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:
# Square numbers in range and turn into list
lst = [x**2 for x in range(0,11)]
lst
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
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
We can also perform nested list comprehensions, for example:
lst = [ x**2 for x in [x**2 for x in range(11)]]
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.