Python basics-list, python-list

Python basics-list, python-list

List is an ordered set that allows you to add and delete elements at any time.

Knowledge point:

Add	Append (),. insert ()
Delete	. Pop (1)
Query	Classmates [-1]
Change	Classmates [1] = 'sara'
Additional	S = ['python', 'java', ['asp ', 'php'], 'scheme'], s [2] [1]

 

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Create:

>>> classmates = ['Michael', 'Bob', 'Tracy']>>> classmates['Michael', 'Bob', 'Tracy']

 

Add:

List is a variable ordered table. Therefore, you can append an element to the end of the list: >>> classmates.append('Adam')>>> classmates['Michael', 'Bob', 'Tracy', 'Adam'] You can also insert an element to a specified position, for example, index number1Location: >>> classmates.insert(1, 'Jack')>>> classmates['Michael', 'Jack', 'Bob', 'Tracy', 'Adam']

 

 

 

 

 

Delete:

To delete the element at the end of the list, usepop()Method: >>> classmates.pop()'Adam'>>> classmates['Michael', 'Jack', 'Bob', 'Tracy'] To delete the element at the specified position, usepop(i)Method, whereiIs the index location: >>> classmates.pop(1)'Jack'>>> classmates['Michael', 'Bob', 'Tracy']

 

 

 

 

 

 

 

 

 

Query:

>>> len(classmates) 3 >>> classmates[0]'Michael'>>> classmates[1]'Bob'>>> classmates[2]'Tracy'>>> classmates[3]Traceback (most recent call last): File "<stdin>", line 1, in <module >>> classmates[-1]'Tracy' And so on, you can get 2nd to the last and 3rd to the last: >>> classmates[-2]'Bob'>>> classmates[-3]'Michael'>>> classmates[-4]Traceback (most recent call last): File "<stdin>", line 1, in <module>IndexError: list index out of range Of course, the last 4th will be out of the border.

 

 

 

 

 

 

 

 

 

 

Change:

To replace an element with another element, you can directly assign a value to the corresponding index location: >>> classmates[1] = 'Sarah'>>> classmates['Michael', 'Sarah', 'Tracy']

 

 

 


Additional:

The Data Types of the elements in the list can also be different, for example:

>>> L = ['Apple', 123, True]

The list element can also be another list, for example:

>>> s = ['python', 'java', ['asp', 'php'], 'scheme']>>> len(s)4

Note:sThere are only four elements, of whichs[2]It is also a list, which is easier to understand if it is split and written:

>>> p = ['asp', 'php']>>> s = ['python', 'java', p, 'scheme']

To get'php'Writablep[1]Ors[2][1], SosIt can be seen as a two-dimensional array, similar to 3D, four-dimensional ...... Array, but rarely used.

If no element exists in a list, it is an empty list with a length of 0:

>>> L = []>>> len(L)0