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📛 NAME

itertools - Functional tools for creating and using iterators.

🚀 Quick Reference

Use Case	Command	Description
🔢 Infinite counter	count(start, step)	Generate arithmetic progression
🔁 Cycle elements	cycle(iterable)	Repeat sequence indefinitely
🔗 Chain iterables	chain(*iterables)	Concatenate multiple iterables
🚫 Filter false	filterfalse(pred, iterable)	Items where predicate is false
🪟 Sliding pairs	pairwise(iterable)	Overlapping pairs from input
📊 Group by key	groupby(iterable, key)	Consecutive groups by key
✖️ Cartesian product	product(*iterables)	All combinations of elements

📖 DESCRIPTION

♾️ Infinite iterators

• count(start=0, step=1) → start, start+step, start+2*step, ...
• cycle(p) → p0, p1, ... plast, p0, p1, ...
• repeat(elem [,n]) → elem, elem, elem, ... endlessly or up to n times

🛑 Iterators terminating on the shortest input sequence

• accumulate(p[, func]) → p0, p0+p1, p0+p1+p2
• chain(p, q, ...) → p0, p1, ... plast, q0, q1, ...
  chain.from_iterable([p, q, ...]) → p0, p1, ... plast, q0, q1, ...
• compress(data, selectors) → (d[0] if s[0]), (d[1] if s[1]), ...
• dropwhile(pred, seq) → seq[n], seq[n+1], starting when pred fails
• groupby(iterable[, keyfunc]) → sub-iterators grouped by value of keyfunc(v)
• filterfalse(pred, seq) → elements of seq where pred(elem) is False
• islice(seq, [start,] stop [, step]) → elements from seq[start:stop:step]
• pairwise(s) → (s[0],s[1]), (s[1],s[2]), (s[2], s[3]), ...
• starmap(fun, seq) → fun(*seq[0]), fun(*seq[1]), ...
• tee(it, n=2) → (it1, it2 , ... itn) splits one iterator into n
• takewhile(pred, seq) → seq[0], seq[1], until pred fails
• zip_longest(p, q, ...) → (p[0], q[0]), (p[1], q[1]), ...

🧮 Combinatoric generators

• product(p, q, ... [repeat=1]) → cartesian product
• permutations(p[, r])
• combinations(p, r)
• combinations_with_replacement(p, r)

📦 CLASSES

Inheritance: builtins.object

• accumulate
• chain
• combinations
• combinations_with_replacement
• compress
• count
• cycle
• dropwhile
• filterfalse
• groupby
• islice
• pairwise
• permutations
• product
• repeat
• starmap
• takewhile
• zip_longest

🏷️ accumulate

accumulate(iterable, func=None, *, initial=None)

Return series of accumulated sums (or other binary function results).

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ chain

chain(*iterables) → chain object

Return a chain object whose .__next__() method returns elements from the first iterable until it is exhausted, then elements from the next iterable, until all of the iterables are exhausted.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.

🏷️ Class methods

• __class_getitem__(...) from builtins.type — See PEP 585
• from_iterable(iterable, /) from builtins.type — Alternative chain() constructor taking a single iterable argument that evaluates lazily.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ combinations

combinations(iterable, r)

Return successive r-length combinations of elements in the iterable.

combinations(range(4), 3) → (0,1,2), (0,1,3), (0,2,3), (1,2,3)

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.
• __sizeof__(...) — Returns size in memory, in bytes.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ combinations_with_replacement

combinations_with_replacement(iterable, r)

Return successive r-length combinations of elements in the iterable allowing individual elements to have successive repeats.

combinations_with_replacement('ABC', 2) → ('A','A'), ('A','B'), ('A','C'), ('B','B'), ('B','C'), ('C','C')

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.
• __sizeof__(...) — Returns size in memory, in bytes.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ compress

compress(data, selectors)

Return data elements corresponding to true selector elements. Forms a shorter iterator from selected data elements using the selectors to choose the data elements.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ count

count(start=0, step=1)

Return a count object whose .__next__() method returns consecutive values.

Equivalent to:

def count(firstval=0, step=1):
    x = firstval
    while 1:
        yield x
        x += step

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __repr__(self, /) — Return repr(self).

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ cycle

cycle(iterable, /)

Return elements from the iterable until it is exhausted. Then repeat the sequence indefinitely.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ dropwhile

dropwhile(predicate, iterable, /)

Drop items from the iterable while predicate(item) is true. Afterwards, return every element until the iterable is exhausted.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ filterfalse

filterfalse(function, iterable, /)

Return those items of iterable for which function(item) is false. If function is None, return the items that are false.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ groupby

groupby(iterable, key=None)

Make an iterator that returns consecutive keys and groups from the iterable.

iterable — Elements to divide into groups according to the key function.

key — A function for computing the group category for each element. If the key function is not specified or is None, the element itself is used for grouping.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ islice

islice(iterable, stop) → islice object
islice(iterable, start, stop[, step]) → islice object

Return an iterator whose next() method returns selected values from an iterable. If start is specified, will skip all preceding elements; otherwise, start defaults to zero. Step defaults to one. If specified as another value, step determines how many values are skipped between successive calls. Works like a slice() on a list but returns an iterator.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ pairwise

pairwise(iterable, /)

Return an iterator of overlapping pairs taken from the input iterator.

s → (s0,s1), (s1,s2), (s2, s3), ...

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ permutations

permutations(iterable, r=None)

Return successive r-length permutations of elements in the iterable.

permutations(range(3), 2) → (0,1), (0,2), (1,0), (1,2), (2,0), (2,1)

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.
• __sizeof__(...) — Returns size in memory, in bytes.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ product

product(*iterables, repeat=1) → product object

Cartesian product of input iterables. Equivalent to nested for-loops.

For example, product(A, B) returns the same as: ((x,y) for x in A for y in B). The leftmost iterators are in the outermost for-loop, so the output tuples cycle in a manner similar to an odometer (with the rightmost element changing on every iteration).

To compute the product of an iterable with itself, specify the number of repetitions with the optional repeat keyword argument. For example, product(A, repeat=4) means the same as product(A, A, A, A).

product('ab', range(3)) → ('a',0) ('a',1) ('a',2) ('b',0) ('b',1) ('b',2)
product((0,1), (0,1), (0,1)) → (0,0,0) (0,0,1) (0,1,0) (0,1,1) (1,0,0) ...

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.
• __sizeof__(...) — Returns size in memory, in bytes.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ repeat

repeat(object [,times]) → create an iterator which returns the object for the specified number of times. If not specified, returns the object endlessly.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __length_hint__(...) — Private method returning an estimate of len(list(it)).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __repr__(self, /) — Return repr(self).

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ starmap

starmap(function, iterable, /)

Return an iterator whose values are returned from the function evaluated with an argument tuple taken from the given sequence.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ takewhile

takewhile(predicate, iterable, /)

Return successive entries from an iterable as long as the predicate evaluates to true for each entry.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🏷️ zip_longest

zip_longest(iter1 [,iter2 [...]], [fillvalue=None]) → zip_longest object

Return a zip_longest object whose .__next__() method returns a tuple where the i-th element comes from the i-th iterable argument. The .__next__() method continues until the longest iterable in the argument sequence is exhausted and then it raises StopIteration. When the shorter iterables are exhausted, the fillvalue is substituted in their place. The fillvalue defaults to None or can be specified by a keyword argument.

🔧 Methods

• __getattribute__(self, name, /) — Return getattr(self, name).
• __iter__(self, /) — Implement iter(self).
• __next__(self, /) — Implement next(self).
• __reduce__(...) — Return state information for pickling.
• __setstate__(...) — Set state information for unpickling.

⚙️ Static methods

• __new__(*args, **kwargs) from builtins.type — Create and return a new object. See help(type) for accurate signature.

🔧 FUNCTIONS

• tee(iterable, n=2, /) — Returns a tuple of n independent iterators.

📁 FILE

(built-in)

📛 NAME 🚀 Quick Reference 📖 DESCRIPTION 📦 CLASSES 🔧 FUNCTIONS 📁 FILE