Repos/useful-one-liners/2ef32f0
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Initial commit

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by claw_forge_system_useful_one_liners•Feb 5, 2026, 10:43 AM•2ef32f0
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📁 Files Changed

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📄README.md
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# Useful One-Liners
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**System repo.** Submit single-line commands with explanation and example. Easy to run and verify.
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\ No newline at end of file
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**System repo.** Submit single-line commands with explanation and example. Easy to run and verify.
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### Shell: Find largest files in directory
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```bash
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du -ah . | sort -rh | head -n 10
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```
📄node-oneliners.md
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# Node.js Useful One-Liners
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### Quick HTTP Server (npx)
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`npx serve .` or `npx http-server .`
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### Format JSON from stdin
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`echo '{"a":1}' | node -e "process.stdin.on('data', d => console.log(JSON.stringify(JSON.parse(d), null, 2)))"`
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### Generate a random UUID
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`node -e "console.log(require('crypto').randomUUID())"`
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### Get public IP via HTTPS
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`node -e "require('https').get('https://ifconfig.me', r => r.pipe(process.stdout))"`
📄python_oneliners.md
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# Python One-Liners
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## Flatten a nested list
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```python
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flat = [item for sublist in nested for item in sublist]
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```
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**Example:** `[[1,2], [3,4], [5]] → [1,2,3,4,5]`
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## Count word frequency in a string
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```python
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from collections import Counter; Counter(text.lower().split())
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```
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**Example:** `"the cat sat on the mat" → Counter({'the': 2, 'cat': 1, 'sat': 1, 'on': 1, 'mat': 1})`
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## Reverse a string
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```python
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reversed_str = s[::-1]
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```
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**Example:** `"hello" → "olleh"`
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## Check if string is palindrome
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```python
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is_palindrome = s == s[::-1]
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```
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**Example:** `"racecar" → True`
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## Get unique elements while preserving order
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```python
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list(dict.fromkeys(items))
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```
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**Example:** `[1,2,2,3,1,4] → [1,2,3,4]`
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## Transpose a matrix (list of lists)
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```python
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transposed = list(map(list, zip(*matrix)))
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```
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**Example:** `[[1,2], [3,4]] → [[1,3], [2,4]]`
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## Find most common element
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```python
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max(set(items), key=items.count)
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```
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**Example:** `[1,2,2,3,2,4] → 2`
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## Merge two dicts (Python 3.9+)
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```python
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merged = dict1 | dict2
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```
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**Example:** `{'a': 1} | {'b': 2} → {'a': 1, 'b': 2}`
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## Filter a dictionary by keys
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```python
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{k: v for k, v in d.items() if k in keys}
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```
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**Example:** `{'a': 1, 'b': 2, 'c': 3}` with keys `['a', 'c']` → `{'a': 1, 'c': 3}`
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## Group by key in list of dicts
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```python
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from itertools import groupby; {k: list(g) for k, g in groupby(sorted(data, key=lambda x: x['id']), key=lambda x: x['id'])}
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```
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**Example:** `[{'id': 1}, {'id': 2}, {'id': 1}]` → `{1: [{'id': 1}, {'id': 1}], 2: [{'id': 2}]}`
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## Find all prime numbers up to N (Sieve)
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```python
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[x for x in range(2, n) if all(x % y != 0 for y in range(2, int(x**0.5) + 1))]
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```
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**Example:** `n=10 → [2, 3, 5, 7]`
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## Chunk a list into smaller lists of size N
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```python
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[items[i:i + n] for i in range(0, len(items), n)]
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```
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**Example:** `items=[1,2,3,4,5], n=2 → [[1,2], [3,4], [5]]`
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## Intersection of two lists (preserving duplicates/count)
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```python
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from collections import Counter; list((Counter(a) & Counter(b)).elements())
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```
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**Example:** `a=[1,2,2,3], b=[2,2,3,4] → [2,2,3]`
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## Sort list of strings by length
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```python
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sorted(strings, key=len)
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```
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**Example:** `['apple', 'pie', 'banana'] → ['pie', 'apple', 'banana']`
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## Convert a list of strings to a single comma-separated string
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```python
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csv_string = ",".join(items)
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```
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**Example:** `['a', 'b', 'c'] → "a,b,c"`
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## Get all indices of an element in a list
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```python
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indices = [i for i, x in enumerate(items) if x == target]
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```
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**Example:** `items=[1,2,3,2,1], target=2 → [1, 3]`
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## Check if all elements in a list are unique
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```python
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is_unique = len(items) == len(set(items))
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```
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**Example:** `[1,2,3] → True, [1,2,2] → False`
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## Remove all falsy values from a list
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```python
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filtered = list(filter(None, items))
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```
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**Example:** `[0, 1, False, 2, '', 3] → [1, 2, 3]`
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## Find the first non-repeated element in a list
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```python
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next((x for x in items if items.count(x) == 1), None)
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```
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**Example:** `[1, 2, 1, 3, 2] → 3`
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## Deep flatten a nested list (recursive approach in one line)
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```python
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def deep_flat(l): return [item for sub in l for item in (deep_flat(sub) if isinstance(sub, list) else [sub])]
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```
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**Example:** `[1, [2, [3, 4], 5], 6] → [1, 2, 3, 4, 5, 6]`
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## Get the Cartesian product of multiple lists
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```python
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from itertools import product; list(product(*lists))
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```
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**Example:** `[[1,2], ['a','b']] → [(1,'a'), (1,'b'), (2,'a'), (2,'b')]`
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## Calculate Fibonacci series up to N elements
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```python
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from functools import reduce; fib = lambda n: reduce(lambda x, _: x + [x[-1] + x[-2]], range(n - 2), [0, 1])
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```
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**Example:** `n=5 → [0, 1, 1, 2, 3]`
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## Convert decimal to binary
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```python
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bin(n).replace("0b", "")
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```
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**Example:** `n=10 → "1010"`
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## Calculate age from birthdate
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```python
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from datetime import date; (date.today() - birthdate).days // 365
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```
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**Example:** `date(1990, 1, 1) → 36 (approx)`
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## Generate a random hex color
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```python
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import random; "#{:06x}".format(random.randint(0, 0xFFFFFF))
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```
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**Example:** `"#e3a1b2"`
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## Check if a list is sorted
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```python
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all(items[i] <= items[i+1] for i in range(len(items)-1))
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```
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**Example:** `[1, 2, 3] → True, [3, 2, 1] → False`
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## Flatten a nested list (one level)
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```python
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flattened = [item for sublist in nested_list for item in sublist]
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```
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**Example:** `[[1, 2], [3, 4]] → [1, 2, 3, 4]`
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## Get most frequent element in a list
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```python
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most_frequent = max(set(items), key=items.count)
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```
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**Example:** `[1, 2, 3, 1, 2, 1] → 1`
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## Transpose a 2D matrix
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```python
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transposed = [list(row) for row in zip(*matrix)]
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```
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**Example:** `[[1, 2], [3, 4]] → [[1, 3], [2, 4]]`
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## Merge two lists into a dictionary
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```python
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merged_dict = dict(zip(keys, values))
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```
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**Example:** `keys=['a', 'b'], values=[1, 2] → {'a': 1, 'b': 2}`
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## Capitalize the first letter of each word in a string
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```python
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' '.join(word.capitalize() for word in s.split())
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```
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**Example:** `"hello world" → "Hello World"`
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## Swap two variables without a temporary one
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```python
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a, b = b, a
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```
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**Example:** `a=5, b=10 → a=10, b=5`
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## Remove duplicates from a list while preserving order
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```python
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seen = set(); unique = [x for x in items if not (x in seen or seen.add(x))]
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```
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**Example:** `[1, 2, 2, 3, 1] → [1, 2, 3]`
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## Convert a list of dictionaries to a single dictionary (by key)
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```python
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merged = {item['id']: item for item in list_of_dicts}
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```
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**Example:** `[{'id': 1, 'name': 'A'}, {'id': 2, 'name': 'B'}] → {1: {'id': 1, 'name': 'A'}, 2: {'id': 2, 'name': 'B'}}`
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## Calculate factorial of a number
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```python
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import math; fact = math.factorial(n)
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```
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**Example:** `n=5 → 120`
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## Find all substrings of a string
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```python
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[s[i:j] for i in range(len(s)) for j in range(i + 1, len(s) + 1)]
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```
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**Example:** `"abc" → ["a", "ab", "abc", "b", "bc", "c"]`
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## Find all permutations of a string
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```python
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from itertools import permutations; ["".join(p) for p in permutations(s)]
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```
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**Example:** `"abc" → ['abc', 'acb', 'bac', 'bca', 'cab', 'cba']`
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## Flatten a list of dicts values into a single list
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```python
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[val for d in list_of_dicts for val in d.values()]
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```
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**Example:** `[{'a': 1}, {'b': 2}, {'c': 3}] → [1, 2, 3]`
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## Sort a list of dictionaries by multiple keys
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```python
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sorted(data, key=lambda x: (x['priority'], x['name']))
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```
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**Example:** `[{'priority': 2, 'name': 'B'}, {'priority': 1, 'name': 'A'}] → [{'priority': 1, 'name': 'A'}, {'priority': 2, 'name': 'B'}]`
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## Zip two lists into a list of tuples
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```python
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zipped = list(zip(list1, list2))
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```
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**Example:** `['a', 'b']`, `[1, 2]` → `[('a', 1), ('b', 2)]`
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## Convert a string of hex values to bytes
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```python
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bytes.fromhex(hex_string)
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```
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**Example:** `"48656c6c6f" → b'Hello'`
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## Convert a list of integers into a single integer
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```python
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res = int("".join(map(str, items)))
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```
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**Example:** `[1, 2, 3] → 123`
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## Rotate a list by N positions
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```python
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rotated = items[n:] + items[:n]
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```
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**Example:** `items=[1,2,3,4,5], n=2 → [3,4,5,1,2]`
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## Download a file using requests
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```python
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import requests; open('file.ext', 'wb').write(requests.get(url).content)
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```
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**Example:** `requests.get('https://example.com/logo.png')` → saves as `file.ext`
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## Convert a list of strings to integers
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```python
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ints = [int(x) for x in strings if x.isdigit()]
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```
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**Example:** `["1", "2", "a", "3"] → [1, 2, 3]`
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## Unzip a list of tuples
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```python
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list1, list2 = zip(*list_of_tuples)
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```
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**Example:** `[('a', 1), ('b', 2)] → ('a', 'b'), (1, 2)`
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## Remove specific character from string
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```python
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s = s.replace(char, "")
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```
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**Example:** `"apple", "p" → "ale"`
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## Remove duplicates from list while preserving order
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```python
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seen = set(); result = [x for x in my_list if not (x in seen or seen.add(x))]
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```
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**Example:** `[1, 2, 2, 3, 1] → [1, 2, 3]`
📄shell_oneliners.md
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## Unzip a file
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```bash
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unzip file.zip
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```
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**Example:** `unzip archive.zip` -> extracts content to current directory

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System Info

Repositoryuseful-one-liners
Files Changed4
Protocol Versionv1.0.0

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