python built-in functions list (list)

First, a list of list

A queue, a neat team, called the individual element within the list, the list consists of several elements, the element can be any object (numbers, strings, objects, lists, etc.)
Sequential within the list of elements, the index may be used, a linear data structure, [], a list is variable
Differences List list, list, queue, stack of

Second, define and initialize a list of list

list () define an empty list list (iterable) to initialize an iterator list list can not define the size of the beginning
List definition mode: lst = list () or lst = []
Example: lst = [2,6,9, 'ab'] lst = list (range (5))

Third, the access list index

Index, also known as subscript
Positive index: from left to right, starting from 0 in the list each element number
Negative Index: right to left, starting from -1 to list each element number
Positive and negative index can not be out of bounds, otherwise an exception is thrown IndexError, in order to facilitate understanding, can be considered a list arranged from left to right, the left is the head, the tail is on the right, the left is the lower bound, the right is the upper bound
List through an index access methods: list [index], index is an index, the use of parentheses access

Fourth, the list query

1、list.index(value,[start,[stop])

By value value, find elements within the list from the specified range matches, the first match will immediately return to the index, not match, an exception is thrown ValueError
For example:
>>> lst = [2,6,9,'ab']
>>> lst.index(2)
0
>>> lst.index(6,0,3)
1

2、list.count(value)

The number of returns a list of matching value
time complexity
and index count methods are O (n)
With the increase of the size of the list of data and reduced efficiency
len (lst) returns a list of the number of elements
For example:
>>> lst = lst = [2,6,9,9,9,'ab']
>>> lst
[2, 6, 9, 9, 9, 'ab']
>>> lst.count(9)
3

Fifth, modify the list elements

Sixth, the list increased, insert elements

list.append (object): the tail of the list of additional elements, returns None, returns None means no new list generated in situ modification, the time complexity is O (1)
list.insert (index, object) return None, returns None means no new list generated in situ modification, the time complexity is O (1)
Insert index out of bounds: Beyond the upper bound, the tail added, beyond the lower bound, the head added list.extend (iterable) return None, the iterable elements added in, return None, in situ modification
list + list: connecting operation connecting the two lists, a new list, change the original list, the call is essentially __add __ () method
list * list: repeat, present a list of elements is repeated n times, and returns the new list

Seven, remove elements list

list.remove (value): Returns None, find the first value matches the value from left to right, the element is removed, returns None, modified in situ
list.pop ([index]): not specified index to pop an element from the end of the list, specify the index, the index from the pop-up element, the index of bounds error thrown IndexError
list.clear (): Clears the list of all the elements, return None, remaining an empty list

Eight, a list of other actions

list.reversed (): the list of elements reversed, return None, in situ modification
list.sort (key = None, reverse = False): Sorts the elements of the list, in-place modify the default ascending order, reverse = True descending order, it is a key function, specify how the sort key
whether in [3,4] in [1,2, [3,4]]

Nine, copy the list

1, the shadow copy, also called shallow copy: list.copy (), encounters a reference type, just copy a reference to it

Test lst1 = list (range (4)) and lst2 = list (range (4)) are equal?
>>> lst1 = list(range(4))
>>> lst1
[0, 1, 2, 3]
>>> lst2 = list(range(4))
>>> lst2
[0, 1, 2, 3]
>>> lst1 == lst2
True
The above test description, lst1 and lst2 equal, the two lists point to the same reference
Test 1:
>>> lst1 = list(range(4))
>>> lst2 = lst1.copy()
>>> lst1
[0, 1, 2, 3]
>>> lst2
[0, 1, 2, 3]
>>> lst2[2] = 10
>>> lst2
[0, 1, 10, 3]
>>> lst1
[0, 1, 2, 3]
>>> lst1 == lst2
False

2, deep copy: copy module that provides deepcopy