Basic Python Tutorial (iv)

List

This section continues the discussion of the list of different tuples and strings: The list is mutable (mutable)---- can change the contents of the list, and the list has many useful, specialized methods.

the list function can split a string into a list.

>>> List (‘Chongshi ") ["  C ",  ' h",  ' o ",  ' n ",  "g", h",  "i "            

Changing the list: assigning values to an element

For example, we want to assign a value to an element in a list.

>>> x =[1,2,3,4]>>> x[2]=18>>> x[1, 2, 4] 

Delete Element

It is also easy to remove elements from the list, using the DELE statement.

>>> names = [‘Zhangsan','Lisi','Wangwu','sunliu']>>> del names [2]>>> names['zhangsan', 'Lisi', 'sunliu']  

Shard Assignment :

>>> name = List (‘Huzi‘) >>>name[‘H‘,‘U‘,‘Z‘,‘I‘]>>> Name[2:]=list ( "dazhi " >>> Name[ ' h",  "u" d  ", " a ', z",  ' h",  i "         

NameThe content is "Huzi", starting with the first 3 characters (2), replacing"da "with"zi"and being expanded"zhi", so the new The content of name is "Hudazhi".

List method

A method is a function that is closely related to some object, which can be a list, a number, or a string or other type of object, which in general is called by the method:

Object. Method (Parameter)

A method call is similar to a function call.

1,append

The Append method is used to append a new object to the end of the list:

>>> ABC = []>>> abc.append (4) >>> abc[1, 2, 3, 4]  

2. Count

The Count method counts the number of occurrences of an element in the list:

>>> [‘to ",  '  Be ",  ' or",  ' not ",  "to", 

3, Extend

The Extend method can append multiple values from another sequence at the end of the list at once. To extend an existing list with a new list:

>>> a = []>>> b = [4,5,6]>>> a.extend (b) >>> a[1, 2, 3, 4, 5, 6]
         

4. Index

The index method is used to find the first occurrence of a value from a list.

>>> Knights = [‘We‘,‘Is ",  ' the",  ' kninghts ",  "who",  ' say",  ni "]>>> Knights.index (  "who"  ) 4>>> knights[4] " who "         

5. Insert

The Insert method is used to insert an object into the list:

>>> numbers = [1,2,3,5,6,7]>>> Numbers.insert (3,'four') >>>'  Four', 5, 6, 7]       

6. Pop

The pop method removes an element from the list (the last one by default) and returns the value of the element:

>>> x = []>>> x.pop () 3>>> x[1, 2]>>> x.pop (0) 1>> > x[2]     

7. Remove

The Remove method is used to remove the first occurrence of a value in the list:

>>> x = [‘To‘,‘Be‘,‘Or‘,‘Not‘,‘To ", " be ' to  ",  ' or",  ' not ",  ' to ",  "be"]      

8, Reverse

The revers method stores the elements in the list in reverse

>>> x = []>>> x.reverse () >>> x[3, 2, 1]  

9. Sort

The sort method is used to sort the list at the original location. "Sort in place" changes the original list so that the elements can be sorted in a certain order.

>>> x = [4,6,2,1,7,9]>>> x.sort () >>> x[1, 2, 4, 6, 7, 9]  

Tuples: Immutable sequences

Tuples, like lists, are also a sequence. The only difference is that tuples cannot be changed. The syntax for creating tuples is simple: if you split some values with commas, you automatically create tuples.

>>>(1, 2, 3) >>> (  Square) # the tuple (1, 2, 3) >>> ()  # empty tuple ()      

How do you implement a tuple that contains a value? The method is a bit peculiar ---- must be comma-even if there is only one value:

>>>, (3) >>> (20+1)>>> 3 * (+/-) 63>>> (20+1 ,      (+)

Tuple function

the function of the tuple function is basically the same as the list function: Take a sequence as a parameter and convert it to a tuple.

>>> tuple ([C-C]) (1, 2, 3) >>> tuple ('ABC')('a'b') C') >>> tuple ((+)) (1, 2, 3)           

Basic Python Tutorial (iv)