list

Use the keyword [] to define the list. Here is a

fruits = ["Apple", "Banana", "Pear"]

The elements in the access list are accessed using subscripts. Like java, subscripts are calculated from 0, but python supports negative indexes, which start from the last bit

print(fruits[0])
print(fruits[-1])
print(fruits[-2])

Apple
Pear
Banana

Note that the subscript here cannot exceed the index. The maximum value of the fruits index is 2 and the minimum value is - 3. If it exceeds this range, the subscript will be out of bounds

Modify element

Elements can be modified by direct assignment using subscripts

fruits = ["Apple", "Banana", "Pear"]
print(fruits[0])
fruits[0] = "watermelon"
print(fruits[0])

Apple
watermelon

Add element

Add append to the tail

fruits = ["Apple", "Banana", "Pear"]
fruits.append("watermelon")
print(fruits)

['Apple', 'Banana', 'pear', 'watermelon']

Add insert in the middle

insert(index,value) receives two values. Index represents the current location to be queried, and value represents the value

fruits = ["Apple", "Banana", "Pear"]
fruits.insert(1, "watermelon")
print(fruits)

['Apple', 'watermelon', 'Banana', 'pear']

Delete element del

del receives a parameter that specifies the index of the element

fruits = ["Apple", "Banana", "Pear"]
del fruits[0]
print(fruits)

['Banana', 'pear']

Delete element pop

Pop will delete the last bit of the element and return the deleted element. It is more appropriate to say pop-up

fruits = ["Apple", "Banana", "Pear"]
print(fruits.pop())
print(fruits)

Pear
['Apple', 'Banana']

List operation

sort() sort

fruits = ["Apple", "Banana", "Pear"]
print(fruits)
fruits.sort()
print(fruits)

['Apple', 'Banana', 'pear']
['pear', 'Apple', 'Banana']

sorted() temporary sort

sort() will change the original list, but sorted() will not change the original list

fruits = ["Apple", "Banana", "Pear"]
print(sorted(fruits))
print(fruits)

['pear', 'Apple', 'Banana']
['Apple', 'Banana', 'pear']

reverse() reverse order

Reverse the list

fruits = ["Apple", "Banana", "Pear"]
print(fruits)
fruits.reverse()
print(fruits)

['Apple', 'Banana', 'pear']
['pear', 'Banana', 'Apple']

List length len

Returns the length of the list

fruits = ["Apple", "Banana", "Pear"]
print(len(fruits))

3

Traversal list

fruits = ["Apple", "Banana", "Pear"]

for f in fruits:
    print(f)

Apple
Banana
Pear

Create a list of values

range(1,5)

It starts from the specified element, but does not contain the ending number. If you do not specify the starting size, it starts from 0 by default, and you can also specify the interval

nums = list(range(0, 5))
for n in nums:
    print(n)

0
1
2
3
4

Make numerical statistics on the list

What are the maximum, minimum, and maximum values in the list

nums = list(range(0, 5))
print(min(nums))
print(max(nums))
print(sum(nums))

0
4
10

section

[1:2] specify two numbers. The first is the start position, and the second parameter is the end position. If you do not specify the default last bit, if you do not specify either, copy the list directly

nums = list(range(0, 5))
print(nums[0:2])
print(nums[0:])
print(nums[:])

[0, 1]
[0, 1, 2, 3, 4]
[0, 1, 2, 3, 4]

tuple

Tuples are very similar to lists, using ()

heros = ("top", "Fight wild")
print(heros[0])

top

The value of a tuple cannot be changed, but it can be reassigned

heros = ("top", "Fight wild")
heros[0] = "ad"

So you won't report an error

heros = ("top", "Fight wild")
heros = ("ad")

Dictionaries

Here comes the universal key value pair, defined by {}

heros = {"top":"Dema", "Fight wild":"spider"}
print(heros)
print(heros["top"])

{'Shangdan': 'dema', 'beat the wild': 'spider'}
Dema

To access an element, you can also use get() to receive two parameters, the first parameter is the subscript, the key in the key value pair, and the second is the value returned if there is no corresponding key

heros = {"top": "Dema", "Fight wild": "spider"}
print(heros)
print(heros.get("top", "No corresponding element exists"))
print(heros.get("mid", "No corresponding element exists"))

{'Shangdan': 'dema', 'beat the wild': 'spider'}
Dema
No corresponding element exists

Traversal dictionary

Traverse all. items()

heros = {"top": "Dema", "Fight wild": "spider"}

for k,v in heros.items():
    print(k + "---" + v)

Shangdan dema
Playing wild - Spider

Traversal keys()

heros = {"top": "Dema", "Fight wild": "spider"}

for k in heros.keys():
    print(k)

top
Fight wild

Traversal values()

heros = {"top": "Dema", "Fight wild": "spider"}

for v in heros.values():
    print(v)

top
Fight wild