[Python Learning]—Python Basic Grammar (6)

1. Data container

Data container in Python: a data type that can hold multiple pieces of data. Each element contained can be any type of data, such as strings, numbers, Boolean, etc.

2. list list

subscript index of list

Subscripts for nested lists

my_list=['aaa',1,'True']
print(my_list[0])
print(my_list[1])
print(my_list[2])

my_list=['aaa',1,'True']
print(my_list[-1])
print(my_list[-2])
print(my_list[-3])

(1), index method

(2) Modification of the list

列表【下标】=值

(3), insert method

(4) Appending a single element at the end

(5) Appending elements in batches at the end

(6) Element deletion

my_list=['aaa','bbb','ccc']
del my_list[0]
print(my_list)

(7) remove method

Remove the first occurrence of an element in the list

my_list=['aaa','bbb','ccc']
my_list.remove('aaa')
print(my_list)

(8) clear method

(9) count method

Count the number of elements in a list

(10), len method

3. Overview of list methods

4. Practice

list_mess=[21,25,21,23,22,20]
list_mess.append(31)
print(list_mess)

fir_list=list_mess[0]
print(fir_list)
last=list_mess[-1]
print(last)

index=list_mess.index(31)
print(index)

5. Traversal of lists

my_list=['beijing','shanghai','hangzou']
index=0
while index<len(my_list):
    ele=my_list[index]
    print(f"列表的元素{ele}")
    index+=1

my_list=[1,2,3,4]
for ele in my_list:
    print(f"列表的元素有{ele}")
    

# list=[]
# list_num=[1,2,3,4,5,6,7,8,9,10]
# for ele in list_num:
#     if (ele%2==0):
#         list.append(ele)
#
# print(f"从列表{list_num}中取出偶数，组成新的列表{list}")

index=0
list=[]
list_num=[1,2,3,4,5,6,7,8,9,10]
while(index < len(list_num)):
    ele=list_num[index]
    index+=1
    if(ele%2==0):
        list.append(ele)
print(f"从列表{list_num}中取出偶数，组成新的列表{list}")

(f"从列表{list_num}中取出偶数，组成新的列表{list}")

6. Tuple

Tuple definition: Use parentheses to define a tuple, and use commas to separate each data. The data can be of different data types.

7. Tuple related operations

tu1=(1,2,3,3,3)
num=tu1.index(2)
print(num)

tot=tu1.count(3)
print(tot)

num2=len(tu1)
print(num2)

tu1=(1,2,3,3,3)
num=tu1.index(2)
print(num)

tot=tu1.count(3)
print(tot)

num2=len(tu1)
print(num2)

index=0
while( index<len(tu1)):
    print(tu1[index])
    index+=1

for ele in tu1:
    print(ele)

Characteristics of tuples

8. String

Summary of commonly used operations on strings

Characteristics of strings

my_str="caicai studying"
result=my_str.count("caicai")
print(result)

resu1=my_str.replace(" ","|")

print(resu1)

resu2=resu1.split("|")
print(resu2)

9. Sequence

The operation on the sequence will not affect itself, but will result in a new sequence.

my_list=[0,1,2,3,4]
result1=my_list[1:4:1]
print(result1)

my_tuples=(1,2,3,4,5)
result2=my_tuples[::2]
print(result2)

my_str="1234556"
result3=my_str[::2]
print(result3)

my_str="希望今年有个offer，希望好运"
result1=my_str[::-1][5:10]
print(result1)


result2=my_str[6:11][::-1]
print(result2)

10. Use of collections

Sets are unordered, so sets do not support subscript index access, but sets, like lists, are allowed to be modified.

Add new element

Remove element

Pick out an element at random

my_set={
    
    "aaa","bbb","ccc"}
ele=my_set.pop()
print(ele)//aaa

Clear collection

Difference of sets

set1={
    
    1,2,3}
set2={
    
    2,3,4}
set3=set1.difference(set2)#集合1有而集合2没有的
print(set3)#{1}

Eliminate the difference set of sets

set1={
    
    1,2,3}
set2={
    
    1,3,4}

set1.difference_update(set2)
print(set1)#{2}
print(set2)#{1,3,4}

Merge collection

set1={
    
    1,2,3}
set2={
    
    2,3,4}

set3=set1.union(set2)
print(set3)#{1,2,3,4}

Number of statistical collections

set1={
    
    1,2,3,4,5}
res=len(set1)
print(res)#5

Summary of commonly used functions of collection

How to iterate over a collection

• You can use a for loop to traverse
• You cannot use a while loop because subscript indexing is not supported.

Collection features

my_list1=[1,2,3,4,3,3,5]
list1=set()
for x in my_list1:
    list1.add(x)
    print(list1)#{1,2,3,4,5}

10. Dictionary

Definition of dictionary: {} is also used, but the stored elements are key-value pairs, as follows:

my_dir={
    
    "张三":19,"李四":20,"王五":21}
age=my_dir["张三"]
print(age)//19

11. Common operations on dictionary

Summary of commonly used dictionary operations

my_dir={
    
    
    "王力宏":
    {
    
    
       "部门":"科技部",
        "工资":3000,
        "级别":1
    },
"王力":
    {
    
    
       "部门":"科技部",
        "工资":3500,
        "级别":3
    },
"王宏":
    {
    
    
       "部门":"研发部",
        "工资":4000,
        "级别":2
    }

}
print(my_dir)

12. Classification and comparison of data containers

13. General statistical functions of data containers

Universal sorting function for containers (the sorted result will become a list object)

my_lisy= [2,1,11,3,5]
tota=sorted(my_lisy)
print(tota)//[1, 2, 3, 5, 11]