List comprehensions provide an more Pythonic and alternative way (i.e instead of using map and filter) in which to express a list.
There are 3 components to a list comprehension. The expression, the for loop and the optional condition.
As you can see below, by changing the expressions and enclosing brackets to your expression you can express your list as either a list, set, list of tuples or dictionary.
>>> # LIST
>>> [x for x in range(50) if x < 25]
[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]
>>> # SET
>>> {x for x in range(50) if x < 25}
set([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])
>>> # TUPLE
>>> [(x,x+1) for x in range(50) if x < 25]
[(0, 1), (1, 2), (2, 3), (3, 4), (4, 5), (5, 6), (6, 7), (7, 8), (8, 9), (9, 10), (10, 11), (11, 12), (12, 13), (13, 14), (14, 15), (15, 16), (16, 17), (17, 18), (18, 19), (19, 20), (20, 21), (21, 22), (22, 23), (23, 24), (24, 25)]
>>> # DICT
>>> {x:x+1 for x in range(50) if x < 25}
{0: 1, 1: 2, 2: 3, 3: 4, 4: 5, 5: 6, 6: 7, 7: 8, 8: 9, 9: 10, 10: 11, 11: 12, 12: 13, 13: 14, 14: 15, 15: 16, 16: 17, 17: 18, 18: 19, 19: 20, 20: 21, 21: 22, 22: 23, 23: 24, 24: 25}
- How to Configure a BIND Server on Ubuntu - March 15, 2018
- What is a BGP Confederation? - March 6, 2018
- Cisco – What is BGP ORF (Outbound Route Filtering)? - March 5, 2018
Want to become a programming expert?
Here is our hand-picked selection of the best courses you can find online:
Python Zero to Hero course
Python Pro Bootcamp
Bash Scripting and Shell Programming course
Automate with Shell Scripting course
The Complete Web Development Bootcamp course
and our recommended certification practice exams:
AlphaPrep Practice Tests - Free Trial