Four data structures: list, tuple, set, and dict

list list

1. Python has four basic data types: list, set, tuple, and dict. Think of them as memory storage solutions. You can first understand the basic additions, deletions, differences, and changes .
2. List is the most basic data structure in Python. The first index is 0, the second index is 1, and so on, the last index is -1.
3. The data items in the list do not need to have the same type, and the data supports duplication.
4. To create a list, simply enclose the different data items separated by commas in square brackets.

Add, delete, check, modify operation

l = [100, 'A', True, 3.14, "A"]
print(l, len(l), type(l))
# 追加列表
l.append('python')
# 插入列表
l.insert(0, 'java')
print(l)  # java、100、A、True、3.14、A、python
# 移除列表数据,默认是最后一个元素,并且返回该元素的值
print(l.pop(-1))
# 该方法没有返回值但是会移除列表中的某个值的第一个匹配项
l.remove("A")
# 删除指定下标的对象
del l[-1]
# 更新指定下标的值
l[2] = False
# 遍历列表数据
for temp in l:
    # java 100 False 3.14
    print(temp, end=' ')

• Interception and splicing operations

l = [1,2,3,4,5]
# 切片可以对所有序列(字符串,list,tuple,set)进行操作
print(l[:2],l[2:],l[:])
# 列表拼接操作
l +=[6,7,8,9,10]
# append追加元素
l.append([20,30])

Common function operations

l = [1,1,2,3,4,5,6]
# 统计某个元素在列表中出现的次数
print(l.count(1))
# 从列表中找出某个值第一个匹配项的索引位置
print(l.index(3))
# 反向列表中元素
l.reverse()
print(l)

tuple data type

1. Python tuples are similar to lists, except that the elements of tuples cannot be modified.
2. Use parentheses for tuples and square brackets for lists.
3. Tuple creation is very simple, just add elements in parentheses and separate them with commas.

Read-only tuple operations

tup1 = ('Google', 'Runoob', 1997, 2000);
tup1 = ();  # 创建一个空元组
del tup;    # 不能删除元组中某个元素,但是能删除整个元素

Tuple operations

l = (1, 2, 3)
print(l,type(l),id(l))
print(l[:2])
l2 = l + (4, 5, 6)
print(l2,type(l2),id(l2))
l3 = l * 3
print(l3,type(l3),id(l3))

set collection

1. A set is an unordered sequence of non-repeating elements.
2. Braces {} or set() function to create a collection, note: to create an empty collection you must use set() instead of {}, because {} is used to create an empty dictionary

l = {}  # 空大括号代表字典，而非集合
print(type(l))  # dict
l = set()
print(type(l))  # set

l.add('java')  # 没有下标不存在append
l.add('NET')
l.add('PYTHON')
l.add('NET')  # 如果元素已存在，则不进行任何操作
l.add('python')

for temp in l:
    print(temp, end=' ')

# 随机移除一个元素
print('\n pop移除元素为:', l.pop())

# 移除指定的元素，如果元素不存在，则会发生错误
l.remove('java')

# 移除集合中的元素，且如果元素不存在，不会发生错误
l.discard('oracle')

for temp in l:
    print(temp, end=' ')

• Introduction to dict dictionary

Dictionary is another variable container model, and can store any type of object. Each key value (key=>value) pair of the dictionary is separated by a colon (:), and each pair is separated by a comma (,). The entire dictionary is enclosed in curly braces ({})

1. The key must be unique, but the value need not.
2. The value can take any data type, but the key must be immutable, such as a string, number, or tuple.

dict = {'Name': '小强', 'Age': 7, 'Name': '小菜鸟'}
# 采用中括号，如果key并未找到则会抛出异常，采用get则会显示缺省值
print ("dict['Name']: ", dict.get('name','旺财'))

# 以列表返回一个字典所有的键
for key in d.keys():
    print(key , end=' ')
print()
# 列表返回一个字典所有的值
for val in d.values():
    print(val , end = ' ')

dict = {'Name': '小强', 'Age': 7}
dict['Age'] = 8;               # 更新 Age
dict['School'] = "Python人工智能"     # 添加信息
print ("dict['Age']: ", dict['Age'])
print ("dict['School']: ", dict['School'])

del dict['Name'] # 删除键 'Name'
dict.clear()     # 清空字典
del dict         # 删除字典,功能通常
print(dict)      # name 'dict' is not defined

 

Type feature summary