Lazy
Bases: Generic[T]
Object representing lazy evaluation of called methods.
Calling any method consumes the current Lazy
object. Using the same object
again may cause errors due to the draining of the generator.
Found in qwlist.Lazy
Examples:
>>> qlist = QList([1, 2, 3, 4])
>>> filtered = qlist.filter(lambda x: x < 3)
>>> mapped_str = filtered.map(str)
>>> mapped_float = filtered.map(float)
>>> print(mapped_float.qlist()) # prints [1.0, 2.0]
>>> print(mapped_str.qlist()) # prints []
Source code in src\qwlist\qwlist.py
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|
__init__(gen)
Parameters:
Name | Type | Description | Default |
---|---|---|---|
gen |
Iterable[T]
|
generator used to yield values on collecting items. |
required |
Source code in src\qwlist\qwlist.py
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|
all(mapper=None)
Goes through the entire generator and checks if all elements are Truthy
.
Booly
is a type that evaluates to something that is either True
(Truthy
) or False
(Falsy
).
For example in Python an empty list evaluates to False
(empty list is Falsy
).
Parameters:
Name | Type | Description | Default |
---|---|---|---|
mapper |
Optional[Callable[[T], Booly]]
|
|
None
|
Returns:
Type | Description |
---|---|
bool
|
|
Source code in src\qwlist\qwlist.py
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|
any(mapper=None)
Goes through the entire generator and checks if any element is Truthy
.
Booly
is a type that evaluates to something that is either True
(Truthy
) or False
(Falsy
).
For example in Python an empty list evaluates to False
(empty list is Falsy
).
Parameters:
Name | Type | Description | Default |
---|---|---|---|
mapper |
Optional[Callable[[T], Booly]]
|
|
None
|
Returns:
Type | Description |
---|---|
bool
|
|
Source code in src\qwlist\qwlist.py
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|
batch(size)
Groups elements into batches of given size
. The last batch may have fewer elements.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
size |
int
|
size of one batch. |
required |
Returns:
Type | Description |
---|---|
Lazy[QList[T]]
|
New |
Examples:
>>> Lazy(range(5)).batch(2).collect()
[[0, 1], [2, 3], [4]]
Source code in src\qwlist\qwlist.py
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|
batch_by(grouper)
Batches elements of self
based on the output of the grouper function. Elements are thrown
to the same group as long as the grouper function returns the same key (keys must support equality checks).
When a new key is returned a new batch (group) is created.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
grouper |
Callable[[T], SupportsEq]
|
|
required |
Returns:
Type | Description |
---|---|
Lazy[QList[T]]
|
New |
Examples:
>>> Lazy(['a1', 'b1', 'b2', 'a2', 'a3', 'b3']).batch_by(lambda s: s[0]).collect()
[['a1'], ['b1', 'b2'], ['a2', 'a3'], ['b3']]
>>> Lazy(['a1', 'b1', 'b2', 'a2', 'a3', 'b3']).batch_by(lambda s: s[1]).collect()
[['a1', 'b1'], ['b2', 'a2'], ['a3', 'b3']]
Source code in src\qwlist\qwlist.py
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|
chain(other)
Chains self
with other
, returning a new Lazy[T] with all elements from both iterables.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
other |
Iterable[T]
|
an iterable of elements to be "attached" after self is exhausted. |
required |
Returns:
Type | Description |
---|---|
Lazy[T]
|
New |
Examples:
>>> Lazy(range(0, 3)).chain(range(3, 6)).collect()
[0, 1, 2, 3, 4, 5]
Source code in src\qwlist\qwlist.py
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|
collect()
Goes through elements of self
collecting values into QList
.
Returns:
Type | Description |
---|---|
QList[T]
|
|
Source code in src\qwlist\qwlist.py
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|
cycle()
Returns a new Lazy[T]
that cycles through the elements of self
, which means
on achieving the last element the iteration starts from the beginning. The
returned Lazy
object has no end (infinite iterator) unless self
is empty
in which case cycle returns an empty Lazy
object (empty iterator).
Returns:
Type | Description |
---|---|
Lazy[T]
|
Infinite |
Examples:
>>> Lazy([1, 2, 3]).cycle().take(7).collect()
[1, 2, 3, 1, 2, 3, 1]
Source code in src\qwlist\qwlist.py
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|
enumerate(start=0)
Returns a new Lazy
object with index-value pairs as its elements. Index starts at
the given position start
(defaults to 0).
Parameters:
Name | Type | Description | Default |
---|---|---|---|
start |
int
|
starting index. Defaults to 0. |
0
|
Returns:
Type | Description |
---|---|
Lazy[Tuple[int, T]]
|
New |
Examples:
>>> Lazy(['a', 'b', 'c']).enumerate().collect()
[(0, 'a'), (1, 'b'), (2, 'c')]
Source code in src\qwlist\qwlist.py
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|
filter(pred)
Returns a new Lazy
object containing all values from self
for which
the predicate holds true.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
pred |
Callable[[T], bool]
|
|
required |
Returns:
Type | Description |
---|---|
New |
Examples:
>>> Lazy([0, 1, 2, 3]).filter(lambda x: x < 2).collect()
[0, 1]
Source code in src\qwlist\qwlist.py
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|
flatmap(mapper)
Applies the mapper function to each of the yielded elements and flattens the results.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
mapper |
Callable[[T], Iterable[K]]
|
|
required |
Returns:
Type | Description |
---|---|
Lazy[K]
|
New |
Examples:
>>> Lazy([1, 2]).flatmap(lambda x: [x, x]).qlist()
[1, 1, 2, 2]
Source code in src\qwlist\qwlist.py
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|
flatten()
If self
is a Lazy
object of Iterable[T]
, flatten concatenates all iterables into a
single list and returns a Lazy[T]
object.
Returns:
Type | Description |
---|---|
Lazy[T]
|
Concatenation of all elements from |
Raises:
Type | Description |
---|---|
TypeError
|
when elements of Lazy are not iterables. |
Examples:
>>> Lazy([[1, 2], [3, 4]]).flatten().collect()
[1, 2, 3, 4]
Source code in src\qwlist\qwlist.py
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|
fold(operation, init)
Given the combination operator reduces self
by processing
its constituent parts, building up the final value.
Other names: fold_left, reduce, accumulate, aggregate.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
operation |
Callable[[K, T], K]
|
|
required |
init |
K
|
initial value for the combination operator. |
required |
Returns:
Type | Description |
---|---|
K
|
The final value created from calling the |
Examples:
>>> Lazy([1, 2, 3]).fold(lambda acc, x: acc + x, 0)
6
Source code in src\qwlist\qwlist.py
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|
foreach(action)
Applies the given function to each of yielded elements.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
action |
Callable[[T], None]
|
|
required |
Returns:
Type | Description |
---|---|
|
Source code in src\qwlist\qwlist.py
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|
full_flatten(break_str=True, preserve_type=None)
When self
is an iterable of nested iterables, all the iterables are flattened to a single iterable.
Recursive type annotation of self
may be imagined to look like this: Lazy[T | Iterable[T | Iterable[T | ...]]]
.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
break_str |
bool
|
If |
True
|
preserve_type |
Optional[Type]
|
Type to exclude from flattening (i.e., treated as non-iterable). For example,
setting this to |
None
|
Returns:
Type | Description |
---|---|
Lazy[T]
|
New |
Examples:
>>> Lazy(['abc', ['def', 'ghi']]).full_flatten().collect()
['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']
>>> Lazy(['abc', ['def', 'ghi']]).full_flatten(break_str=False).collect()
['abc', 'def', 'ghi']
>>> Lazy(['abc', ['def', 'ghi']]).full_flatten(preserve_type=list).collect()
['a', 'b', 'c', ['def', 'ghi']]
Source code in src\qwlist\qwlist.py
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|
iter()
Changes self
into Iterator[T]
by calling the iter()
function.
Returns:
Type | Description |
---|---|
Iterator[T]
|
iterator over the elements of |
Source code in src\qwlist\qwlist.py
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|
list()
Goes through elements of self
collecting values into standard Python list
.
Returns:
Type | Description |
---|---|
List[T]
|
Standard Python |
Source code in src\qwlist\qwlist.py
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|
map(mapper)
Returns a new Lazy
object containing all values from self
with
the mapping function applied on them.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
mapper |
Callable[[T], K]
|
|
required |
Returns:
Type | Description |
---|---|
New |
Source code in src\qwlist\qwlist.py
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|
max(key=None)
Returns the biggest element from the iterable. If the key function is not passed, identity
function is used in which case T
must support LessThan
operator.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
key |
Optional[Callable[[T], SupportsLessThan]
|
|
None
|
Returns:
Type | Description |
---|---|
Optional[T]
|
the biggest element of |
Source code in src\qwlist\qwlist.py
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|
merge(other, merger)
Merges self
with other
, maintaining the order of elements based on the merger function. It starts by
taking the first elements from self
and other
, calling the merger function with these elements as arguments.
If the output is True, the first element is yielded; otherwise, the second element is yielded. If self
is
empty, the remaining elements from other
are yielded, and vice versa.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
other |
Iterable[T]
|
an iterable to be merged with |
required |
merger |
Callable[[T, T], bool]
|
|
required |
Returns:
Type | Description |
---|---|
Lazy[T]
|
New |
Examples:
>>> QList([1, 3, 5]).merge([2, 4, 6], lambda left, right: left < right).collect()
[1, 2, 3, 4, 5, 6]
Source code in src\qwlist\qwlist.py
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|
min(key=None)
Returns the smallest element from self
. If the key function is not passed, identity
function is used in which case T
must support LessThan
operator.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
key |
Optional[Callable[[T], SupportsLessThan]
|
|
None
|
Returns:
Type | Description |
---|---|
Optional[T]
|
the smallest element of |
Source code in src\qwlist\qwlist.py
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|
qlist()
Goes through elements of self
collecting values into QList
. Same as calling collect()
.
Returns:
Type | Description |
---|---|
QList[T]
|
|
Source code in src\qwlist\qwlist.py
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|
scan(operation, state)
Given the combination operator creates a new Lazy[K]
object by processing
constituent parts of self
, yielding intermediate steps and building up the final value.
Scan is similar to fold but returns all intermediate states instead of just the final result.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
operation |
Callable[[K, T], K]
|
|
required |
state |
K
|
initial value for the state. |
required |
Returns:
Type | Description |
---|---|
Lazy[K]
|
Lazy[K] with all intermediate steps of the |
Examples:
>>> Lazy([1, 2, 3]).scan(lambda acc, x: acc + x, 0).collect()
[1, 3, 6]
Source code in src\qwlist\qwlist.py
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|
skip(n)
Skips n
first elements of self
.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
n |
int
|
numbers of elements to skip. Should be non-negative. |
required |
Returns:
Type | Description |
---|---|
Lazy[T]
|
New |
Examples:
>>> Lazy(range(10)).skip(2).collect()
[2, 3, 4, 5, 6, 7, 8, 9]
Source code in src\qwlist\qwlist.py
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sum()
Sums all the elements and returns the sum. Returns None
if self
is empty.
Elements of self
must support addition.
Returns:
Type | Description |
---|---|
Optional[SupportsAdd]
|
The sum of all elements of |
Source code in src\qwlist\qwlist.py
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take(n)
Takes n
first elements of self
.
Args:
n (int): numbers of elements to take. Should be non-negative.
Returns:
Type | Description |
---|---|
Lazy[T]
|
New |
Examples:
>>> Lazy(range(10)).take(2).collect()
[0, 1]
Source code in src\qwlist\qwlist.py
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take_while(pred)
Creates a new Lazy that yields elements based on a predicate. Takes a function as an argument.
It will call this function on each element of self
, and yield elements while the function
returns True
. After False
is returned, iteration stops, and the rest of the elements is ignored.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
pred |
Callable[[T], bool]
|
|
required |
Returns:
Type | Description |
---|---|
Lazy[T]
|
A new |
Source code in src\qwlist\qwlist.py
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window(window_size)
Creates a new Lazy
of sliding windows of size window_size
. If window_size
is greater than the total length of self
an empty iterator is returned.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
window_size |
int
|
the size of the sliding window. Must be greater than 0. |
required |
Returns:
Type | Description |
---|---|
Lazy[QList[T]]
|
New |
Source code in src\qwlist\qwlist.py
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|
zip(other)
Combines self
with the given Iterable
elementwise as tuples.
The returned Lazy
objects yields at most the number of elements of
the shorter sequence (self
or other
).
Parameters:
Name | Type | Description | Default |
---|---|---|---|
other |
Iterable[K]
|
iterable to zip with |
required |
Returns:
Type | Description |
---|---|
Lazy[Tuple[T, K]]
|
New Lazy with pairs of elements from |
Examples:
>>> Lazy([1, 2, 3]).zip(['a', 'b', 'c']).collect()
[(1, 'a'), (2, 'b'), (3, 'c')]
Source code in src\qwlist\qwlist.py
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|