Lists are represented by '[]' in python
List query operations
-
slice of list
names = ["a","b","c"] #Define a list with double quotes to indicate the elements of the list, which look like numbers but are actually strings
print(names[0],names[b]) #Slice names[0] represents the first element in the list, names[a] represents the second element in the list, and so on
print(names[:b]) # The slice starts to the third
print(names[-a]) #take the last
print(names[-b]) #the second from the right
print(names[-b:]) #take the last two
output result
a c
['a', 'b']
c
b
['b', 'c']
-
index method - find element position
names = ["a","b","c"]
print(names.index("c"))
print(names[names.index("c")])
output result
2 ##The element whose subscript is 2 is equivalent to the third one in the list
c
-
count method - how many elements are specified in the query list
names = ["a","b","c","c"]
print(names.count("c"))
output result
2
-
reverse method - reverse the list
names = ["a","b","c","c"]
names.reverse()
print(names)
output result
['c', 'c', 'b', 'a']
or
names = ["a","b","c"]
a = names[::-1]
print(a)
output result
['c', 'b', 'a']
-
sort method - list sorting
Rules: special symbols - numbers - uppercase - lowercase
names = ["b","a","c","c"]
names.sort()
print(names)
output result
['a', 'b', 'c', 'c']
-
list step size
names = ["b","a","www","qqq","c","d","e","f"]
print(names[0:-1:2])
print(names [::2]) #From the beginning to the end, take one every other
output result
['b', 'www', 'c', 'e']
['b', 'www', 'c', 'e']
Adding operations to the list
-
append method - appends elements
names = ["a","b","c"]
names.append("4") #追加一个元素
print(names)
output result
['a', 'b', 'c', '4']
-
insert method - inserts an element
names = [ "a" , "b" , "c" ]
names.insert( a , "d" ) #Insert "5" at position a
print (names)
output result
['a', 'd', 'b', 'c']
-
extend method - merges lists
names = ["b","a","c","c"]
names2 = [1,2,3,4]
names.extend(names2)
print(names)
output result
['b', 'a', 'c', 'c', 1, 2, 3, 4]
-
copy method - copy list
names = ["b","a",["www","qqq"],"c","c"]
name2 = names.copy()
print(names)
print(name2)
output result
['b', 'a', ['www', 'qqq'], 'c', 'c']
['b', 'a', ['www', 'qqq'], 'c', 'c']
List modification operations
-
Modify the list
names = ["a","b","c"]
names[1] = "d" #The element with subscript 1 is changed to "d"
print(names)
output result
['a', 'd', 'c']
-
Modify a sublist in a list
names = ["b","a",["www","qqq"],"c","c"]
names[2][0]="Wwe" #The first print(names) in the third element
output result
['b', 'a', ['Wwe', 'qqq'], 'c', 'c']
List delete operation
-
remove ,del,pop delete method
================================Method 1================== ===========
names = ["a","b","c"]
names.remove("a")
print(names)
output result
['b', 'c']
================================Method 2================== ===========
names = ["a","b","c"]
del names[0] #=names.pop(1)
print(names)
output result
['b', 'c']
================================Method 3================== ===========
names = ["a","b","c"]
names.pop() #default remove the last one
print (names)
output result
['a', 'b']
-
clear method - clears the list
names = ["a","b","c","c"]
names.clear()
print(names)
output result
[]