General method of python sequence list

Note: The test environment of this article is python2.7

Note: This article mainly introduces the general method of lists

Testing list

list1 = [1,2,3, 4]

insert method:

Method explanation: Insert the object at the specified position

Parameters:

Parameter 1: index

Parameter 2: object

Code example:

list1.insert(-1,1) #Insert object at the end of the list

list1.insert(0 ,1) #Insert object at the beginning of the list

Return value: None

Note: After the method is executed, the original list list1

pop method is directly modified ：

Method explanation: Delete the element at the specified index

Parameters: If there is no parameter, the default is index -1 (the last member of the list)

Optional parameter one: index

Code example:

eg: s = list1.pop(1),s=list1[1] before deletion

Return value: deleted index Element

Note 1: When the index does not exist, an out-of-bounds error will be thrown

Note 2: The pop method can implement stack operations

eg:list1.append (list1.pop())

extend method:

Method explanation: Insert the sequence at the end of the list

Parameters:

Parameter 1: Sequence

Code example:

list2 = [1]

list1.extend(list2)

Return value: None

Note: Directly modify the original list list1, often used to connect lists, eg: list1 = list1+list2

index method:

Method explanation: return Specify the position where the element first appears in the list

Parameters:

Parameter 1: object

Parameter 2: startindex (optional, default 0)

Parameter 3: endindex (optional)

Code example:

list1[0] = 1

then list1.index(1) = 0

If you want to output the index of the specified position of the specified object, you need to use the other two parameters

index(objetc,startindex,endindex)

startindex start index

endindex End index

Note: When the object does not exist, an error will be thrown

append method:

Method explanation: Insert data at the end of the list

Parameter:

Parameter 1: object

Code example:

list1.append(1)

Return value: None

count method:

Method explanation: Returns the number of times the specified object appears in the list

Parameters:

Parameter 1: object

Code example:

ret = list1.count(11)

Return value: ret (int>=0)

Note: It can also be based on the number of returns = 0, to determine that the object is not in the list

remove method:

Method explanation: delete the object that appears first in the list

Parameters:

Parameter 1: object

Return value:

Code example:

list1.count(1)

Note 1: The When there are multiple elements, only the first one will be deleted

Note: When the object does not exist, an error will be thrown. It is best to use the count method and in to make the judgment

reverse method:

Method explanation: Reverse the original list

Parameters:

No parameters

Code example:

list1 .reverse()

Return value: No return value

Note: Directly modify list1 to reverse the sequence

Note: Built-in function reversed (object)

Parameter 1:

Sequence

Code example:

list1 = [1,2,3,4]

list2 = list(reversed(list1))

Return value: iterator

Note: The returned list2 is the reverse sequence of list1, but it will not affect the original sequence list1

Note 2: The effect after conversion is similar to list1[::-1]

sort method:

Method explanation: ascending sequence or Sort in descending order

Code example:

list1.sort()

Note: Sort list1 in ascending order

list1.sort (reverse=True)

Note: Sort list1 in descending order

Note: Built-in function sorted()

Method explanation: Return the original sequence Sorted sequence

Code example:

list2 = sorted(list1)

Note: Sorting in ascending order will not affect the original sequence list1

list2 = sorted(list1,reverse=True)

Note: Sorting in descending order will not affect the original required list1

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