Python Full stack development: List of Python lists

List

Lists are frequently used data types in Python for storing multiple values.

Expressions: separated by commas within [], can hold n any type of value

eg

#Single Typeusers=['Yangli','Yite','Fixd']#multiple types, list nestingusers=['room01',['Yangli', 20,'Music'],['Yite', 20,'Basketball']，]

List common methods and functions

Method

Function

Common operations

eg

Len (list)

# len (list) calculates the length of the list ls = ['a','b','C  ','d'= len (ls)print( Length)# results: 4

Append ()

#append () Appendls = ['a','b','C','D']ls.append ('x')Print(LS)#result: [' A ', ' B ', ' C ', ' d ', ' X ']#Append add an element to the end of the list

Inser (Index,obj)

#Inser (index,obj) Insert: Index inserts the start of the list (must be specified), the element to which obj is insertedls = ['a','b','C','D']ls.insert (0,'x')#Insert in headPrint(LS)#result: [' x ', ' A ', ' B ', ' C ', ' d ']ls= ['a','b','C','D']ls.insert, Len (LS),'x')#Insert at TailPrint(LS)#result: [' A ', ' B ', ' C ', ' d ', ' X ']ls= ['a','b','C','D']ls.insert (2,'x')#Insert obj before an element with the original list index of 2Print(LS)#result: [' A ', ' B ', ' X ', ' C ', ' d ']

Remove ()

 #  remove () removes the first occurrence of a value in the list, no return value  ls = [  " a  , "  b  , "  c  , "  d   " ]ls.remove (  "  C   ") #   Remove C  print  (LS) #   result: [' A ', ' B ', ' d ']  

Pop (index)

#Pop (index) removes the first occurrence of a value in the list without a return valuels = ['a','b','C','D']res= Ls.pop ()#Delete the last element by defaultPrint(LS)#result: [' A ', ' B ', ' C ']Print(RES)#Result: D pop () returns the deleted elementls= ['a','b','C','D']res= Ls.pop (2)#Delete the last element by defaultPrint(LS)#result: [' A ', ' B ', ' d ']Print(RES)#Result: C pop () returns the deleted element

Reverse ()

# reverse ()              #反转列表元素ls = ['a','b',' C ','d']ls.reverse ()print(ls)               #  [' d ', ' C ', ' B ', ' a ']

operator of the list

The + and * operators are similar to strings. The + sign is used for the combined list, and the * number is used for repeating lists.

# + *LS1 = ['a', 2,'C']LS2= [1,'y','Z']LS3= LS1 +LS2Print(LS3)#results: [' A ', 2, ' C ', 1, ' Y ', ' z ']Print(ls1*3)#results: [' A ', 2, ' C ', ' A ', 2, ' C ', ' A ', 2, ' C ']

In similar to string in use

#In #判断元素是否存在列表中ls = ['a','b','C','D']Print('C' inchls#TruePrint('x' inchls#False

Comparison of lists ( prerequisites: Must be of the same type to be compared, otherwise error )

#Major premise: only the same type directly compare the size, for the index value of the direct comparison is based on the location one by one corresponding to the comparisonLS1 = ['a','b','C']LS2= ['x','y','Z']LS3= ['A','Z']Print(LS1 > LS2)#Result: FalsePrint(LS1 > LS3)#Result: True

I want to add ...

Slices of a list

For a slice of the list, do not repeat here, refer to the slice of the string.

Python full stack development: Python string slicing

Reading of the list

ls = ['a','b','C','D']#Dependent IndexesI=0 whileI <len (LS): #while循环Print(Ls[i]) I+=1 forIinchrange (len (LS)): #for循环Print(i, ls[i])#do not rely on indexes forIteminchls: #for循环Print(item)

Python Full stack development: List of Python lists