Python Learning Notes (4) collections, tuples, dictionaries, collections

List

Create a list

1. Create directly

　　　　　>>> a = [1, ' 1 ', ' 1.0 ']
>>> A
[1, ' 1 ', ' 1.0 ']

　　　　2. Create with List

>>> A = list ([1, ' 1 ', ' 1.0 ']) >>> A [1, ' 1 ', ' 1.0 '] #括号内可以用小括号, brackets, curly braces.

Method

1. Number of elements in count statistics list

>>> a

[1, 2, 3, 1, 1, 2, 3]
>>> A.count (1)
3

　　　2. Index finds the location of the list where the element is located (the same element in the list returns the first position)

　　　　>>> A

[1, 2, 3, 1, 1, 2, 3]

>>> A.index (1)

0
>>> A.index (2)
1

3. The X in list determines if there are elements in the table, returning True or false

>>> 1 in a

True

>>> 5 in a

False

4. Append add elements to the end of list

　　　　　>>> a = list ([1,2,3,1,1,2,3])

>>> A.append (4)
>>> A
[1, 2, 3, 1, 1, 2, 3, 4]

5. Insert add element at specified position in list

>>> a.insert (0, 5)
>>> A
[5, 1, 2, 3, 1, 1, 2, 3, 4]

6. Extends () adds the value of the B list after the A list

　　>>> B = [5, 6, 7]

>>> A.extend (b)

>>> A
[5, 1, 2, 3, 1, 1, 2, 3, 4, 5, 6, 7]

7. Modifying list values

>>> a[0] = ' 5 '

　　　　　>>> A

[' 5 ', 1, 2, 3, 1, 1, 2, 3, 4, 5, 6, 7]

8. Delete list values

Pop () Delete the element and return the deleted value by default delete the last element, you can specify a location to delete

　　　　　　>>> A.pop ()

7

>>> A.pop (0)

' 5 '

Remove () deletes the specified element when there are multiple identical elements when the first one in the list is deleted

　　　　　　>>> A

　　　　　　[1, 2, 3, 1, 1, 2, 3, 4, 5, 6]

>>> A.remove (3)
>>> A
[1, 2, 1, 1, 2, 3, 4, 5, 6]

　　　　　　　Del Specify location delete element or delete list

　　　　　　>>> A

[1, 2, 1, 1, 2, 4, 5, 6]
>>> del A[1]
>>> A
[1, 1, 1, 2, 4, 5, 6]

　　　　　>>> del a

>>> A
Traceback (most recent):
File "<pyshell#49>", line 1, in <module>
A
Nameerror:name ' A ' is not defined

Clear () empties the elements in the list

' >>> a

[1, 1, 1, 2, 4, 5, 6]
>>> A.clear ()
>>> A
[]

　　　　　　

　　　　　　　　

　　　　　　

　　　　　　

　　　　　　

　　　　　　

　　　　　　

　　　　

　　　　

　　　　

　　　　　　

Python Learning Notes (4) collections, tuples, dictionaries, collections