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Python One-Liners & Tips
Common Python one-liners, tricks, and utilities for quick development tasks.
| Action | Command | Details |
|---|---|---|
| List comprehension | [x**2 for x in range(10)] |
Generate a list of squares from 0 to 9. |
| Reverse string | 'hello'[::-1] |
Reverse the string 'hello' to 'olleh'. |
| Sort list | sorted([3,1,2]) |
Return a sorted copy of the list. |
| Count items | collections.Counter(list) |
Count frequency of items in a list. Requires 'import collections'. |
| Merge dicts | {**dict1, **dict2} |
Merge two dictionaries (Python 3.5+). |
| Swap values | a, b = b, a |
Swap the values of variables a and b. |
| Check even | lambda x: x % 2 == 0 |
Anonymous function to check if a number is even. |
| Read file | open('file.txt').read() |
Read entire file content as a string. |
| Write file | open('file.txt', 'w').write('Hello') |
Write 'Hello' to a file, overwriting it. |
| HTTP request | import requests; requests.get(url).text |
Perform a GET request using the requests library. |
| JSON handling | import json; json.loads(data) |
Parse JSON string into Python objects. |
| Timing | import time; start=time.time() |
Record start time for execution timing. |
| Filter list | list(filter(lambda x: x > 5, items)) |
Filter items greater than 5. |
| Lambda map | list(map(lambda x: x*2, items)) |
Double each item in a list. |
| Set comprehension | {x for x in items if x > 0} |
Create a set of positive items. |
| Dictionary comprehension | {k:v for k,v in iterable} |
Construct a dictionary using comprehension. |
| Flatten list | [y for x in list_of_lists for y in x] |
Flatten a list of lists into a single list. |
| Check if file exists | import os; os.path.exists('file.txt') |
Check presence of a file. |
| Print formatted string | f'Name: {name}, Age: {age}' |
Use f-strings for inline variable substitution. |