156 commands · 9 cheat sheets · Python

Data and Serialization master quick reference

Browse 156 commands from 9 focused cheat sheets on page 1 of 1. Each example opens its matching detailed section.

Data and Serialization · 19 commands

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

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

Data and Serialization · 13 commands

Python Regular Expressions Cheat Sheet

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Use	Syntax	Examples
Compile a pattern	`pattern = re.compile(r'\d{4}-\d{2}-\d{2}')`	View examples
Search anywhere	`match = pattern.search(text)`	View examples
Match from start	`match = pattern.match(text)`	View examples
Validate the whole string	`match = pattern.fullmatch(text)`	View examples
Capture a group	`value = match.group(1)`	View examples
Named capture	`r'(?P<year>\d{4})-(?P<month>\d{2})'`	View examples
Non-capturing group	`r'(?:https?\|ftp)://'`	View examples
Iterate matches	`for match in pattern.finditer(text): print(match.span())`	View examples
Collect matches	`values = pattern.findall(text)`	View examples
Split by pattern	`parts = re.split(r'\s,\s', text)`	View examples
Replace matches	`clean = re.sub(r'\s+', ' ', text).strip()`	View examples
Verbose pattern	`pattern = re.compile(r'''...''', re.VERBOSE)`	View examples
Ignore case	`pattern = re.compile(r'error', re.IGNORECASE)`	View examples

Data and Serialization · 17 commands

Python Text Encoding and Unicode Cheat Sheet

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Use	Syntax	Examples
Encode UTF-8	`payload = text.encode('utf-8')`	View examples
Decode UTF-8	`text = payload.decode('utf-8')`	View examples
Use strict decoding	`text = payload.decode('utf-8', errors='strict')`	View examples
Open UTF-8 text	`with open(path, 'r', encoding='utf-8') as stream: text = stream.read()`	View examples
Write stable LF newlines	`with open(path, 'w', encoding='utf-8', newline='\n') as stream: stream.write(text)`	View examples
Wrap a binary stream	`text_stream = io.TextIOWrapper(binary_stream, encoding='utf-8', newline='')`	View examples
Normalize canonical composition	`normalized = unicodedata.normalize('NFC', text)`	View examples
Check normalization	`ok = unicodedata.is_normalized('NFC', text)`	View examples
Build a caseless key	`key = unicodedata.normalize('NFC', text).casefold()`	View examples
Lowercase for presentation	`lowered = text.lower()`	View examples
Read a code point	`number = ord(character)`	View examples
Create a character	`character = chr(number)`	View examples
Read a Unicode name	`name = unicodedata.name(character, 'UNNAMED')`	View examples
Replace malformed input	`text = payload.decode('utf-8', errors='replace')`	View examples
Preserve OS bytes	`text = payload.decode(filesystem_encoding, errors='surrogateescape')`	View examples
Create a streaming decoder	`decoder = codecs.getincrementaldecoder('utf-8')(errors='strict')`	View examples
Finish a decode stream	`tail = decoder.decode(b'', final=True)`	View examples

Data and Serialization · 20 commands

Python XML Parsing and Generation Cheat Sheet

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Use	Syntax	Examples
Parse an XML value	`root = ET.fromstring(xml_bytes)`	View examples
Parse an XML file	`tree = ET.parse(path)`	View examples
Catch malformed XML	`except ET.ParseError as error: report(error.position)`	View examples
Create an expanded name	`tag = '{urn:books}title'`	View examples
Query with a prefix map	`items = root.findall('b:item', {'b': 'urn:books'})`	View examples
Choose a serialization prefix	`ET.register_namespace('b', 'urn:books')`	View examples
Find one matching element	`item = root.find('./item[@id="a"]')`	View examples
Find matching elements	`items = root.findall('.//item')`	View examples
Iterate matching descendants	`for item in root.iter('item'): consume(item)`	View examples
Append a child element	`child = ET.SubElement(parent, 'item', {'id': item_id})`	View examples
Set element text	`child.text = value`	View examples
Remove a child	`parent.remove(child)`	View examples
Serialize to text	`xml_text = ET.tostring(root, encoding='unicode')`	View examples
Write UTF-8 XML	`tree.write(path, encoding='utf-8', xml_declaration=True)`	View examples
Canonicalize XML	`canonical = ET.canonicalize(xml_data=xml_text)`	View examples
Iterate completed elements	`events = ET.iterparse(source, events=('end',))`	View examples
Release processed content	`element.clear()`	View examples
Create a pull parser	`parser = ET.XMLPullParser(events=('start', 'end'))`	View examples
Inspect the Expat version	`version = pyexpat.EXPAT_VERSION`	View examples
Bound XML input bytes	`if len(xml_bytes) > MAX_XML_BYTES: raise ValueError('XML too large')`	View examples

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