在 Python 中,列表是:
以下是在 Python 中创建列表的示例。
# empty list empty = [] # list of strings listOfSubjects = ['physics', 'chemistry', "mathematics"] # list of numbers listOfIds = [0, 1, 2, 3, 4] # list of mixed types miscList = [0, 'one', 2, 'three'] # list of lists lists = [ ['A', 'B', 'C'], ['D', 'E', 'F'] ]
追加(项目)
方法。插入(搜索,项目)
方法。如果 指数
大于列表大小,则将项目添加到列表末尾。在这种情况下不会抛出任何错误。charList = [] #empty list charList.append("a") charList.append("b") print (charList) # ['a', 'b'] charList.insert(3, "c") print (charList) # ['a', 'b', 'c'] charList.insert(10, "d") # No error print (charList) # ['a', 'b', 'c', 'd']
列表 [m : n]
returns sublist starting at index 米
(included) and ending at index n
(not included).
米
,则假定其值为零。n
,则选择范围直到列表的大小。numList = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] print( numList[0] ) # 0 print( numList[1:5] ) # [1, 2, 3, 4] print( numList[ : 3] ) # [0, 1, 2] print( numList[7 : ] ) # [7, 8, 9] print( numList[-8:-5] ) # [2, 3, 4] - Reverse traversal
要更改列表中的任何特定它/,请使用项目的索引位置并为其分配一个新值。
charList = ["a", "b", "c"] charList [2] = "d" print (charList) # ['a', 'b', 'd']
我们可以使用 for循环 在 Python 中循环遍历列表。
charList = ["a", "b", "c"] for x in charList: print(x) # a # b # c
使用 '在'
关键字来确定列表中是否存在指定的项目。
charList = ["a", "b", "c"] if "a" in charList: print("a is present") # a is present if "d" in charList: print("d is present") else: print("d is NOT present") # d is NOT present
使用 长度()
函数查找给定列表的长度或大小。
charList = ["a", "b", "c"] x = len (charList) print (x) # 3
要从列表中删除项目,请使用四种方法之一。我们可以根据我们拥有的关于要删除的项目的信息来选择适当的删除方法。
去掉()
– 按值删除项目流行音乐()
– 从列表末尾删除项目;或从指定的索引位置。清除()
– 从列表中删除所有项目。的
– 该关键字需要List中要删除的项目的索引。它在列表中搜索指定的项目并根据它的值将其删除。
charList = ["a", "b", "c"] charList.remove("c") print (charList) # ['a', 'b']
它通过它的索引删除指定的项目。如果未提供索引,它会从列表中删除最后一项。
charList = ["a", "b", "c", "d"] charList.pop() # removes 'd' - last item print (charList) # ['a', 'b', 'c'] charList.pop(1) # removes 'b' print (charList) # ['a', 'c']
它清空列表。
charList = ["a", "b", "c", "d"] charList.clear() print (charList) # []
It can be used to 按索引从列表中删除项目. We can use it to 删除整个列表 as well.
charList = ["a", "b", "c", "d"] del charList[0] print (charList) # ['b', 'c', 'd'] del charList print (charList) # NameError: name 'charList' is not defined
我们可以使用 “+”
运算符或 延长()
函数在 Python 中连接两个给定的列表。
charList = ["a", "b", "c"] numList = [1, 2, 3] joinedList = charList + numList print (joinedList) # ['a', 'b', 'c', 1, 2, 3] charList.extend(numList) print (charList) # ['a', 'b', 'c', 1, 2, 3]
在列表末尾添加一个元素。
charList = ["a", "b", "c"] charList.append("d") print (charList) # ["a", "b", "c", "d"]
从列表中删除所有元素。
charList = ["a", "b", "c"] charList.clear() print (charList) # []
返回列表的副本。
charList = ["a", "b", "c"] newList = charList.copy() print (newList) # ["a", "b", "c"]
返回具有指定值的元素数。
charList = ["a", "b", "c"] x = charList.count('a') print (x) # 1
将列表的元素添加到当前列表的末尾。
charList = ["a", "b", "c"] numList = [1, 2, 3] charList.extend(numList) print (charList) # ['a', 'b', 'c', 1, 2, 3]
返回具有指定值的第一个元素的索引。
charList = ["a", "b", "c"] x = charList.index('a') print (x) # 0
在指定位置添加一个元素。
charList = ["a", "b", "c"] charList.insert(3, 'd') print (charList) # ['a', 'b', 'c', 'd']
删除列表指定位置或末尾的元素。
charList = ["a", "b", "c", "d"] charList.pop() # removes 'd' - last item print (charList) # ['a', 'b', 'c'] charList.pop(1) # removes 'b' print (charList) # ['a', 'c']
删除具有指定值的项目。
charList = ["a", "b", "c", "d"] charList.remove('d') print (charList) # ['a', 'b', 'c']
反转列表中项目的顺序。
charList = ["a", "b", "c", "d"] charList.reverse() print (charList) # ['d', 'c', 'b', 'a']
默认情况下按升序对给定列表进行排序。
charList = ["a", "c", "b", "d"] charList.sort() print (charList) # ["a", "b", "c", "d"]
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阅读更多:
Python——列表与元组
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