How to generate sequences in Python?

List comprehensions in python are useful for such tasks. These are very powerful expressions that you can use to generate sequences in a very concise and efficient manner. For example, if you want first 100 integers from 0, you can use −

Example

a = [i for i in range(100)]
print(a)

Output

This will give the output −

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65,
66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86,87,
88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]

Example

Want the squares for first 10 even numbers? You can get it using −

a = [i * i for i in range(20) if i % 2 == 0]
print(a)

Output

This will give the output −

[0, 4, 16, 36, 64, 100, 144, 196, 256, 324]

These expressions can get much more powerful once you know how to use them.