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Introduction to the list
Think about it:
The strings learned earlier can be used to store a string of information, so think about it, how to store the names of all the students in our class?
Is it feasible to define 100 variables, and each variable stores a student's name? Is there a better way?
Answer: list
the list
1. The format of the list
Define the format of the column:[元素1, 元素2, 元素3, ..., 元素n]
The variable tmp is of type list
tmp = ['xiaoWang',180, 65.0]
Elements in a list can be of different types
2. Use subscripts to get list elements
namesList = ['xiaoWang','xiaoZhang','xiaoHua']
print(namesList[0])
print(namesList[1])
print(namesList[2])
result:
xiaoWang
xiaoZhang
xiaoHua
List Data Manipulation
Our operations on variable data (for example, lists, databases, etc.) generally include four aspects: adding, deleting, modifying, and checking.
1. Add elements
There are several ways to add elements:
appendAdd elements at the endinsertInsert an element at the specified positionextendmerge two lists
append
appendwill add the new element to the end of the list
# 定义变量A，默认有3个元素
A = ['xiaoWang','xiaoZhang','xiaoHua']
print("-----添加之前，列表A的数据-----A=%s" % A)
# 提示，并添加元素
temp = input('请输入要添加的学生姓名:')
A.append(temp)
print("-----添加之后，列表A的数据-----A=%s" % A)
insert
insert(index, object)Insert the element object before the specified position index
strs = ['a','b','m','s']
strs.insert(3,'h')
print(strs) # ['a', 'b', 'm', 'h', 's']
extend
By extendadding elements from another collection to a list one by one
a = ['a','b','c']
b = ['d','e','f']
a.extend(b)
print(a) # ['a', 'b', 'c', 'd', 'e', 'f'] 将 b 添加到 a 里
print(b) # ['d','e','f'] b的内容不变
2. Modify elements
We access list elements by specifying a subscript, so when modifying an element, just assign a value to the specified list subscript.
# 定义变量A，默认有3个元素
A = ['xiaoWang','xiaoZhang','xiaoHua']
print("-----修改之前，列表A的数据-----A=%s" % A)
# 修改元素
A[1] = 'xiaoLu'
print("-----修改之后，列表A的数据-----A=%s" % A)
3. Find elements
The so-called search is to check whether the specified element exists, and to check the location of the element, which mainly includes the following methods:
inandnot inindexandcount
The common method of searching in, not in Python is:
in(exists), if exists then the result is True, else is False
not in(does not exist), if not exists then the result is True, otherwiseFalse
# 待查找的列表
nameList = ['xiaoWang','xiaoZhang','xiaoHua']
# 获取用户要查找的名字
findName = input('请输入要查找的姓名:')
# 查找是否存在
if findName in nameList:
print('在列表中找到了相同的名字')
else:
print('没有找到')
Result 1: (found)
Result 2: (not found)
illustrate:
inAs long as the method can be used, not init is also used in the same way, but not inthe judgment is that it does not exist
index, count
indexIt is used to find the location of the element, and an error will be reported if it is not found; countit is used to count the number of occurrences of an element. They are used in the same way as in strings.
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. Delete elements
It is analogous to real life, if a student transfers a class, then the name of the student after this entry should be deleted; this function of deleting is often used in development.
Common ways to delete list elements are:
del: Delete according to subscriptpop: delete the last elementremove: Delete according to the value of the element
of the
movieName = ['加勒比海盗','骇客帝国','第一滴血','指环王','霍比特人','速度与激情']
print('------删除之前------movieName=%s' % movieName)
del movieName[2]
print('------删除之后------movieName=%s' % movieName)
pop
movieName = ['加勒比海盗','骇客帝国','第一滴血','指环王','霍比特人','速度与激情']
print('------删除之前------movieName=%s' % movieName)
movieName.pop()
print('------删除之后------movieName=%s' % movieName)
remove
movieName = ['加勒比海盗','骇客帝国','第一滴血','指环王','霍比特人','速度与激情']
print('------删除之前------movieName=%s' % movieName)
movieName.remove('指环王')
print('------删除之后------movieName=%s' % movieName)
5. Sorting (sort, reverse)
sortThe method is to rearrange the list in a specific order, the default is from small to large, and the parameters reverse=Truecan be changed to reverse order, from large to small.
reverseThe method is to reverse the list.
a = [1, 4, 2, 3]
a.reverse() # 逆置，不排序
a.sort() # 默认从小到大排序
a.sort(reverse=True) # 从大到小排序
practise
Please remove words = ['hello','',','good','hi','','yes','','no']all empty strings in the list.
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