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tuple
Python's tuples are similar to lists, except that the elements of the tuple cannot be modified. Use parentheses for tuples and square brackets for lists.
aTuple = ('et',77,99.9)
aTuple
1. Access tuples
Second, modify the tuple
Explanation: It is not allowed to modify the data of the tuple in python, including deleting the elements.
Three, count, index
index and count are used in the same way as in strings and lists
a = ('a', 'b', 'c', 'a', 'b')
a.index('a', 1, 3) # 注意是左闭右开区间
a.index('a', 1, 4)
a.count('b')
a.count('d')
4. Define a tuple with only one data
To define a tuple with only one element, you need to write a comma after the only element
a = (11)
type(a)
a = (11,) # 只有一个元素的元组，必须要在元素后写一个逗号
type(a)
5. Swap the values of two variables
The first way, using intermediate variables
a = 4
b = 5
c = 0
c = a
a = b
b = c
print(a)
print(b)
The second way is direct exchange.
a, b = 4, 5
a, b = b, a
print(a)
print(b)
dictionary introduction
1. Disadvantages of lists
When the stored data needs to be added and deleted dynamically, we generally use lists, but lists sometimes encounter some troubles.
nameList = ['xiaoZhang', '男', '木匠'];
nameList[2] = '铁匠'
nameList = ['xiaoWang', 18, '男', '铁匠']
nameList[3] = 'xiaoxiaoWang'
Is there a way to not only store multiple data, but also locate the required element when accessing the element is very convenient?
answer:
dictionary
2. The use of dictionaries
Define the format of the dictionary: {key 1: value 1, key 2: value 2, key 3: value 3, ..., key n: value n}
The variable info is a dictionary type:
info = {
'name':'班长', 'id':100, 'sex':'f', 'address':'地球亚洲中国上海'}
info['name']
illustrate:
- Dictionaries, like lists, can also store multiple data
- When looking for an element in the list, it is based on the subscript; when looking for an element in the dictionary, it is based on the 'name' (that is, the value in front of the colon: for example, 'name', 'id', 'sex')
- Each element of the dictionary consists of 2 parts, key: value. For example 'name':'squad leader', 'name' is the key, 'squad leader' is the value
- Keys can use immutable data types such as numbers, Boolean values, and tuples, but it is generally customary to use strings
- The key in each dictionary is unique. If there are multiple keys, the subsequent value will overwrite the value corresponding to the previous key.
- In custom:
- Lists are more suitable for storing similar data such as multiple products, multiple names, and multiple times;
- Dictionaries are more suitable for storing different information about a product, different information about a person, and such different data.
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