Welcome to pyLINQ’s documentation!

This library extends regular python lists to make them easier to filter and sort. Typical list comprehensions such as [x for x in list] can quickly grow out of control for complicated behaviors. pyLINQ solves this by replacing all features of list comprehensions with a series of methods that act on a list.

Here is how easy it is to use:

>>> my_list = List([1,-9,5,2,1])
>>> my_list.select("abs(x)").where("x>3") # Get elements where the absolute value is greater than 3.
[9,5]
>>> my_list.first("x % 2 == 0") # Get the first even number
2
>>> nameList = List(['harry','tina','jeff','hank','john','tom','steve'])
>>> nameList.groupby("x[0]") # Group list elements by first letter in name.
[{'h': ['harry', 'hank']}, {'t': ['tina', 'tom']}, {'j': ['jeff', 'john']}, {'s': ['steve']}]
>>> nameList.orderby("x[0]").takewhile("x[0] < 'm'") # Get all names that come before letter 'm'.
['harry', 'hank', 'jeff', 'john']
List of Methods for List Object
Method Name Description Output
any Returns true if any elements matches expression bool
all Returns true if all elements matches expression bool
concat Combines two lists into a single list List
count Returns the number of elements that match expression int
distinct Returns all elements that are not duplicates List
duplicate Returns all elements that are duplicates List
element Returns the element at a specific index element
except_set Returns all elements except if they are in a second list List
first Returns the first element that matches an expression element
groupby Groups all value by a certain key List
intersect Returns all elements common between two lists List
last Returns the last element that matches an expression element
max Returns the max element of the list element
min Returns the min element of the list element
oftype Returns all elements that match a certain type List
orderby Sort the elements List
select Perform an operation/function on list elements List
skipwhile Return all elements after an expression is true List
sum Return the sum of all elements float
takewhile Return all elements before an expression is false List
union Return the combination of two lists List
where Return all elements that meet an expression List

Example Usage

>>> int_list = List([2,4,6,5])
>>> other_int_list = List([1,2,2,3,4,4,5])
>>> # Sum examples
>>> other_int_list.sum("x > 3") # Sum using conditional statement x > 3
(4 + 4 + 5) = 13
>>> other_int_list.sum("x - 2") # Sum using operation x - 2
(-1 + 0 + 0 + 1 + 2 + 2 + 3) = 7
>>> # chaining expressions example
>>> other_int_list.where("x % 2 != 0").select("x**2").max() # finding the maximum of the square of the odds
max(1,9,25) = 25
>>> # counting
>>> int_list.concat(other_int_list).count("x % 2 == 0") # counting the number of evens in both lists
count(2,4,6,2,2,4,4) = 7

List Object

class List(data=None)

Object which extends python list object to include LINQ style queries.

all(expression)

Checks to see if all items in a list meet a conditional criteria. E.g. List.all(“x > 0”).

Parameters:expression (str or LambdaType) – The expression to apply to the List object, which must be a conditional statement. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:a bool that is true if all elements satisfy the applied expression.
any(expression)

Checks to see if any items in a list meet a conditional criteria. E.g. List.any(“x > 0”).

Parameters:expression (str or LambdaType) – The expression to apply to the List object, which must be a conditional statement. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:a bool that is true if any elements satisfy the applied expression.
append(val)

S.append(value) – append value to the end of the sequence

clear() → None -- remove all items from S
concat(other)

Adds all the elements of another List object onto the calling List object. E.g. List1.concat(List2)

Parameters:other (List) – Another List instance to concatinate with the calling List.
Returns:a new List object that is the concatination of self and other.
count(expression=None)

Counts the number of items in a list that meet a conditional criteria. E.g. List.count(“x > 0”).

Parameters:expression (str or LambdaType or None) – The expression to apply to the List object, which must be a conditional statement. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:an integer representing the number of elements that satisfy the applied expression.
distinct(expression=None)

Checks to see if any items in a list meet a conditional criteria, and also removes duplicates. E.g. List.distinct(“x > 0”).

Parameters:expression (str or LambdaType or None) – The expression to apply to the List object, which must be a conditional statement. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:a new List object that results from the applied expression.
duplicate(expression=None)

Checks to see if any items in a list meet a conditional criteria, but only if they are duplicate items. E.g. List.duplicate(“x > 0”).

Parameters:expression (str or LambdaType or None) – The expression to apply to the List object, which must be a conditional statement. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:a new List object that results from the applied expression.
element(number)

Returns the item at a specified index. E.g. List.element(0)

Parameters:number (int) – The index to get the item from.
Returns:an item from the list or None if index is out of range.
except_set(other)

Removes all instances from a list that exist in another list exept for duplicates. E.g. List1.except_set(List2)

Parameters:other (List) – Another List instance to compare entries with the calling List.
Returns:a new List object that contains all items in self, except any item that exist in other.
first(expression=None)

Finds the first item in a list that meets a conditional criteria. E.g. List.first(“x > 0”).

Parameters:expression (str or LambdaType or None) – The expression to apply to the List object, which must be a conditional statement. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:an item from the list or None if nothing is found.
groupby(expression)

Uses a parameter of that data to group all entries according to key values. E.g. List.groupby(“x[‘key’]”).

Parameters:expression (str or LambdaType) – The expression to apply to the List object. Can either take a string (“x[0]”) or a lambda expression (lambda x : x[0]).
Returns:a new List object that results from the applied expression.
insert(ii, val)

S.insert(index, value) – insert value before index

intersect(other)

Returns all entries that are common between two lists without duplicates. E.g. List1.intersect(List2)

Parameters:other (List) – Another List instance to compare entries with the calling List.
Returns:a new List object that contains all items that exist in both self and other.
last(expression=None)

Finds the last item in a list that meets a conditional criteria. E.g. List.last(“x > 0”).

Parameters:expression (str or LambdaType or None) – The expression to apply to the List object, which must be a conditional statement. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:an item from the list or None if nothing is found.
max(expression=None)

Finds the maximum value item in a list. Optionally, the item can be applied to a conditional criteria. E.g. List.max(“x > 0”) or List.max(“x**2”).

Parameters:expression (str or LambdaType or None) – The expression to apply to the List object. Can also be an operation or function to apply to elements. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:an item from the list or None if nothing is found.
min(expression=None)

Finds the minimum value item in a list. Optionally, the item can be applied to a conditional criteria. E.g. List.min(“x > 0”) or List.min(“x**2”).

Parameters:expression (str or LambdaType or None) – The expression to apply to the List object. Can also be an operation or function to apply to elements. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:an item from the list or None if nothing is found.
oftype(elementType)

Checks to see if any items in a list are of a certain type. E.g. List.oftype(int)

Parameters:elementType (str or type) – The expression to apply to the List object. Can either take a string “int”,”dict”,”List”, etc. or a type.
Returns:a new List object that contains only items of the specified type.
orderby(expression=None, reverse=False)

Orders the items in a list by a certain value. Optionally, the item can be applied to a conditional criteria. E.g. List.orderby(“x > 0”) or List.orderby(“len(x)”).

Parameters:
  • expression (str or LambdaType or None) – The expression to apply to the List object, which must be a conditional statement. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
  • reverse (bool) – True if the list should be descending. False if the list should be ascending.
Returns:

a new List object that results from the applied expression.
pop([index]) → item -- remove and return item at index (default last).

Raise IndexError if list is empty or index is out of range.

remove(val)

S.remove(value) – remove first occurrence of value. Raise ValueError if the value is not present.

select(expression)

Applies an operator or function to each item in the list. E.g. List.select(“len(x)”).

Parameters:expression (str or LambdaType) – The expression to apply to the List object. Can either take a string (“x**2”) or a lambda expression (lambda x : x**2).
Returns:a new List object that results from the applied expression.
skipwhile(expression)

Returns all elements after the first item in the list that fails to meet a conditional criteria. E.g. List.skipwhile(“x > 0”).

Parameters:expression (str or LambdaType) – The expression to apply to the List object, which must be a conditional statement. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:a new List object that results from the applied expression.
sum(expression=None)

Finds the sum of all values in a list. Optionally, the item can be applied to a conditional criteria. E.g. List.sum(“x > 0”) or List.sum(“x**2”)

Parameters:expression (str or LambdaType or None) – The expression to apply to the List object. Can also be an operation or function to apply to elements. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:an item from the list or None if nothing is found.
takewhile(expression)

Returns all elements before the first item in the list that fails to meet a conditional criteria. E.g. List.takewhile(“x > 0”).

Parameters:expression (str or LambdaType) – The expression to apply to the List object, which must be a conditional statement. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:a new List object that results from the applied expression.
union(other)

Returns all entries for two Lists except for any duplicates. E.g. List1.union(List2)

Parameters:other (List) – Another List instance to compare entries with the calling List.
Returns:a new List object that contains all items in self and other, except any duplicates.
where(expression)

Checks to see if any items in a list meet a conditional criteria. E.g. List.where(“x > 0”).

Parameters:expression (str or LambdaType) – The expression to apply to the List object, which must be a conditional statement. If no expression is supplied, then function acts on the whole list. Can either take a string (“x > 0”) or a lambda expression (lambda x : x > 0).
Returns:a new List object that results from the applied expression.

Indices and tables