888 commands · 53 cheat sheets · 7 subcategories

Python master quick reference — Page 2

Browse 211 commands from 12 focused cheat sheets on page 2 of 5. Each example opens its matching detailed section.

Collections and Iteration · 18 commands

Python Iterators and Generators Cheat Sheet

Use	Syntax	Examples
Create an iterator	`iterator = iter(values)`	View examples
Advance an iterator	`value = next(iterator)`	View examples
Use an exhaustion default	`value = next(iterator, None)`	View examples
Consume with a loop	`for value in iterable: print(value)`	View examples
Add indexes	`for index, value in enumerate(values, start=1): print(index, value)`	View examples
Pair iterables	`for name, score in zip(names, scores, strict=True): print(name, score)`	View examples
Create a lazy expression	`squares = (number * number for number in numbers)`	View examples
Filter lazily	`even = (number for number in numbers if number % 2 == 0)`	View examples
Yield a value	`yield value`	View examples
Delegate iteration	`yield from iterable`	View examples
End a generator	`return`	View examples
Compose lazy stages	`result = sum(value for value in source if value > 0)`	View examples
Materialize values	`cached = list(generator)`	View examples
Stop when any value matches	`found = any(value > 100 for value in values)`	View examples
Take a lazy slice	`first_five = islice(iterable, 5)`	View examples
Chain iterables	`combined = chain(first, second)`	View examples
Generate a counter	`identifiers = count(start=1000, step=10)`	View examples
Close a generator	`generator.close()`	View examples

Collections and Iteration · 19 commands

Python itertools, functools, and operator Cheat Sheet

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Use	Syntax	Examples
Concatenate iterables lazily	`items = chain(first, second)`	View examples
Flatten one iterable level	`items = chain.from_iterable(groups)`	View examples
Slice an iterator	`page = islice(source, start, stop, step)`	View examples
Create fixed-size batches	`chunks = batched(source, 3)`	View examples
Require complete batches	`chunks = batched(source, 3, strict=True)`	View examples
Iterate adjacent pairs	`edges = pairwise(values)`	View examples
Compute running totals	`totals = accumulate(values)`	View examples
Accumulate with a function	`products = accumulate(values, operator.mul, initial=1)`	View examples
Fork an iterator	`left, right = tee(source, 2)`	View examples
Group adjacent equal keys	`groups = groupby(records, key=operator.itemgetter('team'))`	View examples
Select with a Boolean mask	`selected = compress(data, selectors)`	View examples
Build a Cartesian product	`coordinates = product(rows, columns)`	View examples
Choose without ordering	`pairs = combinations(values, 2)`	View examples
Create an item lookup	`by_score = operator.itemgetter('score')`	View examples
Create an attribute lookup	`by_name = operator.attrgetter('profile.name')`	View examples
Create a method call	`normalize = operator.methodcaller('strip')`	View examples
Reduce to one value	`total = reduce(operator.add, values, 0)`	View examples
Pre-bind call arguments	`parse_hex = partial(int, base=16)`	View examples
Adapt a comparison function	`key = cmp_to_key(compare)`	View examples

Collections and Iteration · 19 commands

Python Lists Cheat Sheet

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Use	Syntax	Examples
Create a list	`items = ["alpha", "beta"]`	View examples
Create from an iterable	`items = list(range(1, 5))`	View examples
Read the first item	`first = items[0]`	View examples
Read the last item	`last = items[-1]`	View examples
Replace an item	`items[1] = "updated"`	View examples
Append one item	`items.append("beta")`	View examples
Append many items	`items.extend(["gamma", "delta"])`	View examples
Remove by value	`items.remove("beta")`	View examples
Remove the last item	`value = items.pop()`	View examples
Remove by index	`value = items.pop(0)`	View examples
Slice a range	`subset = items[1:4]`	View examples
Slice with a step	`subset = items[::2]`	View examples
Reverse with slicing	`reversed_items = items[::-1]`	View examples
Transform every item	`squares = [x ** 2 for x in items]`	View examples
Filter items	`evens = [x for x in items if x % 2 == 0]`	View examples
Sort the existing list	`items.sort()`	View examples
Create a sorted copy	`result = sorted(items)`	View examples
Sort with a key	`items.sort(key=str.lower)`	View examples
Sort descending	`items.sort(reverse=True)`	View examples

Collections and Iteration · 17 commands

Python Sets and Frozensets Cheat Sheet

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Use	Syntax	Examples
Create a populated set	`colors = {'red', 'green', 'blue'}`	View examples
Create an empty set	`values = set()`	View examples
Remove duplicates	`unique = set(values)`	View examples
Test membership	`if user_id in active_ids: allow()`	View examples
Add one member	`tags.add('python')`	View examples
Add several members	`tags.update(['css', 'html'])`	View examples
Remove a required member	`tags.remove('legacy')`	View examples
Discard if present	`tags.discard('legacy')`	View examples
Combine members	`all_tags = required \| optional`	View examples
Keep shared members	`shared = left & right`	View examples
Subtract members	`missing = required - supplied`	View examples
Keep non-shared members	`changed = before ^ after`	View examples
Test subset	`required <= supplied`	View examples
Test proper subset	`required < supplied`	View examples
Test for no overlap	`left.isdisjoint(right)`	View examples
Build with a comprehension	`lengths = {len(word) for word in words}`	View examples
Create an immutable set	`permissions = frozenset({'read', 'write'})`	View examples

Collections and Iteration · 20 commands

Python Strings Cheat Sheet

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Use	Syntax	Examples
Create a string	`message = "Hello, Python"`	View examples
Create multiline text	`message = "First line\\nSecond line"`	View examples
Count code points	`count = len(message)`	View examples
Read one character	`first = message[0]`	View examples
Slice a range	`prefix = message[:5]`	View examples
Reverse code points	`reversed_text = message[::-1]`	View examples
Trim surrounding whitespace	`clean = raw.strip()`	View examples
Lowercase text	`lowered = name.lower()`	View examples
Normalize for comparison	`matches = left.casefold() == right.casefold()`	View examples
Check for text	`contains = "error" in message`	View examples
Check a prefix	`is_secure = url.startswith("https://")`	View examples
Find a position	`position = message.find("Python")`	View examples
Replace text	`updated = message.replace("draft", "ready")`	View examples
Split fields	`fields = line.split(",")`	View examples
Split once	`key, value = line.split("=", maxsplit=1)`	View examples
Join strings	`path = "/".join(parts)`	View examples
Interpolate values	`message = f"{name} has {count} tasks"`	View examples
Format a number	`label = f"Total: ${total:,.2f}"`	View examples
Encode text	`payload = message.encode("utf-8")`	View examples
Decode bytes	`message = payload.decode("utf-8")`	View examples

Collections and Iteration · 12 commands

Python Tuples, Ranges, and Sequence Operations Cheat Sheet

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Use	Syntax	Examples
Create a tuple	`point = (3, 4)`	View examples
One-item tuple	`single = ('only',)`	View examples
Pack values	`record = name, score, active`	View examples
Unpack positions	`name, score = record`	View examples
Capture the middle	`first, *middle, last = values`	View examples
Count from zero	`range(5)`	View examples
Use start, stop, step	`range(10, 0, -2)`	View examples
Read by index	`last = values[-1]`	View examples
Slice a sequence	`copy = values[start:stop:step]`	View examples
Test membership	`if target in values: handle(target)`	View examples
Iterate with positions	`for index, value in enumerate(values, start=1): print(index, value)`	View examples
Pair sequences strictly	`pairs = zip(names, scores, strict=True)`	View examples

Data and Serialization · 19 commands

Python bytes, bytearray, memoryview, and Binary Data Cheat Sheet

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Use	Syntax	Examples
Create literal bytes	`payload = b'GET / HTTP/1.1\r\n'`	View examples
Create bytes from integers	`payload = bytes([0, 127, 255])`	View examples
Encode Unicode text	`payload = text.encode('utf-8')`	View examples
Read one byte value	`value = payload[0]`	View examples
Copy a byte range	`header = payload[:4]`	View examples
Find a byte marker	`offset = payload.find(b'\r\n')`	View examples
Create a mutable copy	`buffer = bytearray(payload)`	View examples
Replace one byte	`buffer[offset] = value`	View examples
Append binary data	`buffer.extend(chunk)`	View examples
Create a buffer view	`view = memoryview(buffer)`	View examples
Create a read-only view	`readonly = view.toreadonly()`	View examples
Release a view	`view.release()`	View examples
Cast bytes to elements	`words = memoryview(buffer).cast('H')`	View examples
Materialize view values	`values = view.tolist()`	View examples
Pack a portable header	`header = struct.pack('!HI', version, length)`	View examples
Unpack exact-size data	`version, length = struct.unpack('!HI', header)`	View examples
Unpack at an offset	`values = struct.unpack_from('!HI', buffer, offset)`	View examples
Render hexadecimal bytes	`text = payload.hex(sep=' ')`	View examples
Parse hexadecimal text	`payload = bytes.fromhex(text)`	View examples

Data and Serialization · 16 commands

Python Dates, Times, and Time Zones Cheat Sheet

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Use	Syntax	Examples
Create a calendar date	`day = date(2026, 8, 12)`	View examples
Move by elapsed days	`tomorrow = day + timedelta(days=1)`	View examples
Combine date and time	`meeting = datetime.combine(day, time(9, 30))`	View examples
Read the current UTC instant	`now = datetime.now(UTC)`	View examples
Construct an aware datetime	`instant = datetime(2026, 8, 12, 15, tzinfo=UTC)`	View examples
Convert the same instant	`local = instant.astimezone(target_zone)`	View examples
Parse ISO-formatted text	`value = datetime.fromisoformat('2026-08-12T15:30:00+00:00')`	View examples
Emit ISO-formatted text	`text = value.isoformat(timespec='seconds')`	View examples
Parse a declared format	`value = datetime.strptime(text, '%Y-%m-%d %H:%M')`	View examples
Format for display	`label = value.strftime('%Y-%m-%d %H:%M')`	View examples
Load an IANA time zone	`zone = ZoneInfo('America/Sao_Paulo')`	View examples
Decode a POSIX timestamp	`instant = datetime.fromtimestamp(timestamp, tz=UTC)`	View examples
Advance a local schedule	`next_run = local_run + timedelta(days=1)`	View examples
Measure elapsed time	`elapsed = end.astimezone(UTC) - start.astimezone(UTC)`	View examples
Read a duration in seconds	`seconds = duration.total_seconds()`	View examples
Disambiguate a repeated wall time	`later = local.replace(fold=1)`	View examples

Data and Serialization · 17 commands

Python Decimal, Fractions, and Numeric Precision Cheat Sheet

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Use	Syntax	Examples
Compare floats approximately	`same = math.isclose(actual, expected, rel_tol=1e-9, abs_tol=0.0)`	View examples
Sum floats accurately	`total = math.fsum(values)`	View examples
Inspect an exact float ratio	`numerator, denominator = value.as_integer_ratio()`	View examples
Construct from decimal text	`price = Decimal('19.95')`	View examples
Convert an existing float exactly	`value = Decimal.from_float(binary_value)`	View examples
Set local precision	`with localcontext() as ctx: ctx.prec = 12`	View examples
Trap inexact arithmetic	`ctx.traps[Inexact] = True`	View examples
Round to a fixed exponent	`amount = value.quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)`	View examples
Multiply then add once	`result = value.fma(multiplier, addend)`	View examples
Construct an exact fraction	`ratio = Fraction(3, 8)`	View examples
Parse a decimal fraction	`ratio = Fraction('0.125')`	View examples
Approximate with a bounded denominator	`ratio = Fraction(value).limit_denominator(1000)`	View examples
Calculate an arithmetic mean	`average = statistics.fmean(values)`	View examples
Calculate a median	`middle = statistics.median(values)`	View examples
Calculate sample spread	`spread = statistics.stdev(values)`	View examples
Round with Python's built-in policy	`rounded = round(value, ndigits)`	View examples
Format fixed decimal places	`text = f'{value:.2f}'`	View examples

Data and Serialization · 16 commands

Python JSON, CSV, and Data Interchange Cheat Sheet

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Use	Syntax	Examples
Encode a JSON string	`text = json.dumps(value)`	View examples
Decode a JSON string	`value = json.loads(text)`	View examples
Use interoperable value types	`payload = {'ok': True, 'items': [1, 2], 'note': None}`	View examples
Pretty-print deterministically	`text = json.dumps(value, indent=2, sort_keys=True, ensure_ascii=False)`	View examples
Emit compact JSON	`text = json.dumps(value, separators=(',', ':'), ensure_ascii=False)`	View examples
Encode to a text stream	`json.dump(value, stream)`	View examples
Decode from a stream	`value = json.load(stream)`	View examples
Encode a custom type	`text = json.dumps(value, default=encode_custom)`	View examples
Transform decoded objects	`value = json.loads(text, object_hook=decode_custom)`	View examples
Parse decimals exactly	`value = json.loads(text, parse_float=Decimal)`	View examples
Reject non-finite output	`text = json.dumps(value, allow_nan=False)`	View examples
Inspect object key pairs	`value = json.loads(text, object_pairs_hook=reject_duplicates)`	View examples
Read CSV rows	`rows = csv.reader(stream, delimiter=',')`	View examples
Write CSV rows	`writer = csv.writer(stream, lineterminator='\n')`	View examples
Read named CSV fields	`rows = csv.DictReader(stream)`	View examples
Write named CSV fields	`writer = csv.DictWriter(stream, fieldnames=['name', 'note'])`	View examples

Data and Serialization · 18 commands

Python pickle, shelve, and Persistent Objects Cheat Sheet

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Use	Syntax	Examples
Serialize to bytes	`payload = pickle.dumps(value, protocol=pickle.HIGHEST_PROTOCOL)`	View examples
Load trusted bytes	`value = pickle.loads(payload)`	View examples
Write a pickle file	`with open(path, 'wb') as stream: pickle.dump(value, stream, protocol=5)`	View examples
Read the newest protocol	`protocol = pickle.HIGHEST_PROTOCOL`	View examples
Target protocol 4	`payload = pickle.dumps(value, protocol=4)`	View examples
Read the default protocol	`protocol = pickle.DEFAULT_PROTOCOL`	View examples
Customize serialized state	`def __getstate__(self): return {'version': 1, 'value': self.value}`	View examples
Restore validated state	`def __setstate__(self, state): self.value = validate(state)`	View examples
Define a reduction	`def __reduce__(self): return (type(self), (self.value,))`	View examples
Register a type reducer	`copyreg.pickle(ValueType, reduce_value)`	View examples
Use a private reducer table	`pickler.dispatch_table = {ValueType: reduce_value}`	View examples
Emit an external identifier	`def persistent_id(self, obj): return ('Record', obj.key)`	View examples
Resolve an external identifier	`def persistent_load(self, pid): return repository.fetch(pid)`	View examples
Open a shelf	`with shelve.open(path, flag='c', writeback=False) as db: use(db)`	View examples
Persist a mutable update	`value = db[key]; value.append(item); db[key] = value`	View examples
Synchronize a shelf	`db.sync()`	View examples
Disassemble without loading	`python -m pickletools payload.pickle`	View examples
Override global resolution	`def find_class(self, module, name): raise pickle.UnpicklingError('globals forbidden')`	View examples

Data and Serialization · 20 commands

Python Random Sampling and Statistics Cheat Sheet

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Use	Syntax	Examples
Create a local generator	`rng = random.Random(seed)`	View examples
Capture generator state	`state = rng.getstate()`	View examples
Restore generator state	`rng.setstate(state)`	View examples
Draw from range semantics	`value = rng.randrange(start, stop, step)`	View examples
Choose one element	`item = rng.choice(population)`	View examples
Sample without replacement	`items = rng.sample(population, k=3)`	View examples
Sample by relative weight	`draws = rng.choices(population, weights=weights, k=100)`	View examples
Draw a uniform float	`value = rng.uniform(low, high)`	View examples
Draw from a normal model	`value = rng.normalvariate(mu, sigma)`	View examples
Generate random bytes	`token = secrets.token_bytes(32)`	View examples
Generate a URL-safe token	`token = secrets.token_urlsafe(32)`	View examples
Choose securely	`character = secrets.choice(alphabet)`	View examples
Compute an arithmetic mean	`center = statistics.mean(values)`	View examples
Compute a median	`center = statistics.median(values)`	View examples
Find all most-common values	`modes = statistics.multimode(values)`	View examples
Estimate sample spread	`spread = statistics.stdev(sample)`	View examples
Measure population spread	`spread = statistics.pstdev(population)`	View examples
Compute linear correlation	`coefficient = statistics.correlation(xs, ys)`	View examples
Estimate sample quartiles	`cuts = statistics.quantiles(values, n=4, method='exclusive')`	View examples
Summarize observed endpoints	`cuts = statistics.quantiles(values, n=4, method='inclusive')`	View examples

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