List

创建列表

# 使用列表内置函数
list1 = list()
list2 = list() # this is an empty list, no item in the list
print(len(list2)) # 0

# 使用方括号 []
list1 = []
list2 = [] # this is an empty list, no item in the list
print(len(list2)) # 0

len

fruits = ['banana', 'orange', 'mango', 'lemon']                     # list of fruits
vegetables = ['Tomato', 'Potato', 'Cabbage','Onion', 'Carrot']      # list of vegetables
animal_products = ['milk', 'meat', 'butter', 'yoghurt']             # list of animal products
web_techs = ['HTML', 'CSS', 'JS', 'React','Redux', 'Node', 'MongDB'] # list of web technologies
countries = ['Finland', 'Estonia', 'Denmark', 'Sweden', 'Norway']

# Print the lists and its length
print('Fruits:', fruits)
print('Number of fruits:', len(fruits))
print('Vegetables:', vegetables)
print('Number of vegetables:', len(vegetables))
print('Animal products:',animal_products)
print('Number of animal products:', len(animal_products))
print('Web technologies:', web_techs)
print('Number of web technologies:', len(web_techs))
print('Countries:', countries)
print('Number of countries:', len(countries))

lst = ['he', 20, True, {'country':'Finland', 'city':'Helsinki'}] # list containing different data types
print(lst) # ['he', 20, True, {'country': 'Finland', 'city': 'Helsinki'}]

解包列表

lst = ['item1','item2','item3', 'item4', 'item5']
first_item, second_item, third_item, *rest = lst
print(first_item)     # item1
print(second_item)    # item2
print(third_item)     # item3
print(rest)           # ['item4', 'item5']

# First Example
fruits = ['banana', 'orange', 'mango', 'lemon','lime','apple']
first_fruit, second_fruit, third_fruit, *rest = fruits 
print(first_fruit)     # banana
print(second_fruit)    # orange
print(third_fruit)     # mango
print(rest)           # ['lemon','lime','apple']
# Second Example about unpacking list
first, second, third,*rest, tenth = [1,2,3,4,5,6,7,8,9,10]
print(first)          # 1
print(second)         # 2
print(third)          # 3
print(rest)           # [4,5,6,7,8,9]
print(tenth)          # 10
# Third Example about unpacking list
countries = ['Germany', 'France','Belgium','Sweden','Denmark','Finland','Norway','Iceland','Estonia']
gr, fr, bg, sw, *scandic, es = countries
print(gr)          # Germany
print(fr)          # France
print(bg)          # Belgium
print(sw)          # Sweden
print(scandic)     # ['Denmark', 'Finland', 'Norway', 'Iceland']
print(es)          # Estonia

从列表中切片

# Positive Indexing 正索引
fruits = ['banana', 'orange', 'mango', 'lemon']
all_fruits = fruits[0:4] # it returns all the fruits
# this will also give the same result as the one above
all_fruits = fruits[0:] # if we don't set where to stop it takes all the rest
orange_and_mango = fruits[1:3] # it does not include the first index
orange_mango_lemon = fruits[1:] # ['orange', 'mango', 'lemon']
orange_and_lemon = fruits[::2] # here we used a 3rd argument, step. It will take every 2cnd item - ['banana', 'mango']

# Negative Indexing 负索引
fruits = ['banana', 'orange', 'mango', 'lemon']
all_fruits = fruits[-4:] # it returns all the fruits
orange_and_mango = fruits[-3:-1] # it does not include the last index,['orange', 'mango']
orange_mango_lemon = fruits[-3:] # this will give starting from -3 to the end,['orange', 'mango', 'lemon']
reverse_fruits = fruits[::-1] # a negative step will take the list in reverse order,['lemon', 'mango', 'orange', 'banana']

修改列表

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits[0] = 'avocado'
print(fruits)       #  ['avocado', 'orange', 'mango', 'lemon']
fruits[1] = 'apple'
print(fruits)       #  ['avocado', 'apple', 'mango', 'lemon']
last_index = len(fruits) - 1
fruits[last_index] = 'lime'
print(fruits)        #  ['avocado', 'apple', 'mango', 'lime']

检查列表中的项目

fruits = ['banana', 'orange', 'mango', 'lemon']
does_exist = 'banana' in fruits
print(does_exist)  # True
does_exist = 'lime' in fruits
print(does_exist)  # False

向列表添加项目

# append
lst = list()
lst.append(item)

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.append('apple')
print(fruits)           # ['banana', 'orange', 'mango', 'lemon', 'apple']
fruits.append('lime')   
print(fruits)           # ['banana', 'orange', 'mango', 'lemon', 'apple', 'lime']

# insert
lst = ['item1', 'item2']
lst.insert(index, item)

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.insert(2, 'apple') # insert apple between orange and mango
print(fruits)             # ['banana', 'orange', 'apple', 'mango', 'lemon']
fruits.insert(3, 'lime')   
print(fruits)             # ['banana', 'orange', 'apple', 'lime', 'mango', 'lemon']

从列表中删除项目

# remove
lst = ['item1', 'item2']
lst.remove(item)

fruits = ['banana', 'orange', 'mango', 'lemon', 'banana']
fruits.remove('banana')
print(fruits)  # ['orange', 'mango', 'lemon', 'banana'] - this method removes the first occurrence of the item in the list
fruits.remove('lemon')
print(fruits)  # ['orange', 'mango', 'banana']

# pop ()方法删除指定的索引（如果未指定索引，则删除最后一项）
lst = ['item1', 'item2']
lst.pop()       # last item
lst.pop(index)

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.pop()
print(fruits)       # ['banana', 'orange', 'mango']
fruits.pop(0)
print(fruits)       # ['orange', 'mango']

# clear()方法清空列表
lst = ['item1', 'item2']
lst.clear()

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.clear()
print(fruits)       # []

# del 关键字用于删除指定的索引，也可用于删除索引范围内的项目。它也可以完全删除列表
lst = ['item1', 'item2']
del lst[index] # only a single item
del lst        # to delete the list completely

fruits = ['banana', 'orange', 'mango', 'lemon', 'kiwi', 'lime']
del fruits[0]
print(fruits)       # ['orange', 'mango', 'lemon', 'kiwi', 'lime']
del fruits[1]
print(fruits)       # ['orange', 'lemon', 'kiwi', 'lime']
del fruits[1:3]     # this deletes items between given indexes, so it does not delete the item with index 3!
print(fruits)       # ['orange', 'lime']
del fruits
print(fruits)       # This should give: NameError: name 'fruits' is not defined

复制列表

lst = ['item1', 'item2']
lst_copy = lst.copy()

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits_copy = fruits.copy()
print(fruits_copy)       # ['banana', 'orange', 'mango', 'lemon']

加入列表

# Plus Operator (+) 加号运算符 （+）
list3 = list1 + list2

positive_numbers = [1, 2, 3, 4, 5]
zero = [0]
negative_numbers = [-5,-4,-3,-2,-1]
integers = negative_numbers + zero + positive_numbers
print(integers) # [-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5]
fruits = ['banana', 'orange', 'mango', 'lemon']
vegetables = ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']
fruits_and_vegetables = fruits + vegetables
print(fruits_and_vegetables ) # ['banana', 'orange', 'mango', 'lemon', 'Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']

# 使用 extend() 方法 
list1 = ['item1', 'item2']
list2 = ['item3', 'item4', 'item5']
list1.extend(list2)

num1 = [0, 1, 2, 3]
num2= [4, 5, 6]
num1.extend(num2)
print('Numbers:', num1) # Numbers: [0, 1, 2, 3, 4, 5, 6]
negative_numbers = [-5, -4, -3, -2, -1]
positive_numbers = [1, 2, 3, 4, 5]
zero = [0]

negative_numbers.extend(zero)
negative_numbers.extend(positive_numbers)
print('Integers:', negative_numbers) # Integers: [-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5]
fruits = ['banana', 'orange', 'mango', 'lemon']
vegetables = ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']
fruits.extend(vegetables)
print('Fruits and vegetables:', fruits ) # Fruits and vegetables: ['banana', 'orange', 'mango', 'lemon', 'Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']

对列表中的项目进行计数

# count()方法返回项目在列表中出现的次数
lst = ['item1', 'item2']
lst.count(item)

fruits = ['banana', 'orange', 'mango', 'lemon']
print(fruits.count('orange'))   # 1
ages = [22, 19, 24, 25, 26, 24, 25, 24]
print(ages.count(24))           # 3

查找项的索引

# index()方法返回列表中项目的索引
lst = ['item1', 'item2']
lst.index(item)

fruits = ['banana', 'orange', 'mango', 'lemon']
print(fruits.index('orange'))   # 1
ages = [22, 19, 24, 25, 26, 24, 25, 24]
print(ages.index(24))           # 2, the first occurrence

反转列表

# reverse()方法颠倒列表的顺序
lst = ['item1', 'item2']
lst.reverse()

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.reverse()
print(fruits) # ['lemon', 'mango', 'orange', 'banana']
ages = [22, 19, 24, 25, 26, 24, 25, 24]
ages.reverse()
print(ages) # [24, 25, 24, 26, 25, 24, 19, 22]

对列表项进行排序

# sort()此方法修改原始列表
lst = ['item1', 'item2']
lst.sort()                # ascending
lst.sort(reverse=True)    # descending

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.sort()
print(fruits)             # sorted in alphabetical order, ['banana', 'lemon', 'mango', 'orange']
fruits.sort(reverse=True)
print(fruits) # ['orange', 'mango', 'lemon', 'banana']
ages = [22, 19, 24, 25, 26, 24, 25, 24]
ages.sort()
print(ages) #  [19, 22, 24, 24, 24, 25, 25, 26]

ages.sort(reverse=True)
print(ages) #  [26, 25, 25, 24, 24, 24, 22, 19]

# sorted()返回有序列表而不修改原始列表 
fruits = ['banana', 'orange', 'mango', 'lemon']
print(sorted(fruits))   # ['banana', 'lemon', 'mango', 'orange']
# Reverse order
fruits = ['banana', 'orange', 'mango', 'lemon']
fruits = sorted(fruits,reverse=True)
print(fruits)     # ['orange', 'mango', 'lemon', 'banana']