- Video, source code, courseware, software, notes: super comprehensive Python basic introductory tutorial [ten days course] blog notes summary table [dark horse programmer]
- Python basic day03 [string (definition, input and output, common methods), list (definition, basic usage, addition, deletion, modification, nesting), tuple]
table of Contents
Topic 1 [Strengthening training]
Topic 2 [Strengthening training]
Topic 3 [Strengthening training]
Topic 4 [Strengthening training]
Topic 5 [Strengthening training]
Topic 1 [Strengthening training]
Topic 2 [Strengthening training]
Topic 3 [Strengthening training]
Topic 1 [Strengthening training]
Topic 2 [Strengthening training]
1. String
Topic 1 [Strengthening training]
Question stem
If you need to use variables to save the following strings, how do we write the code
Lu Xun said: "I haven't said this sentence"
Training goal
Let students know how to nest strings
Training tips
In python, there are two forms of expression that can be defined as string types. Which two ways are they? Can they be mixed?
Reference plan
Use "" and '' to define the string
Steps
-
To be included in a string
双引号"", the string can be defined with single quotes -
To be included in a string
单引号'', the string can be defined with double quotes
Reference answer
# 在python中，''可以嵌套在""中，用以表示字符串中的字符串
words = "鲁迅说:'我没有说过这句话'"
print(words)
# 还可以使用三引号
words = """鲁迅说:'我没有说过这句话'"""
print(words)
Topic 2 [Strengthening training]
Question stem
Make a simple user information management system: prompt the user to enter the name, age and hobbies in turn, and after the input is completed, the data entered by the user will be displayed at once
Training goal
String declaration string input string output
Training tips
-
In python, declare a variable of string type by "" or"
-
Use the input() function to get data from the keyboard
-
Output string type through %s formatting operator
Reference plan
-
Enter string data through the input function
-
Use string type to save the entered data
-
Use %s to format and output the saved data
Steps
-
Enter string data through the input function
-
Use string type to save the entered data
-
Use %s to format and output the saved data
Reference answer
# 录入数据，并保存在变量中
name = input("请输入姓名：")
age = input("请输入年龄：")
hobby = input("请输入您的爱好：")
# 格式化输出数据
print("您的姓名是%s, 您的年龄是%s， 您的爱好是%s" % (name, age, hobby))
# 使用 f-string
print(f"您的姓名是{name}, 您的年龄是{age}， 您的爱好是{hobby}")
Topic 3 [Strengthening training]
Question stem
The existing strings are as follows, please use slices to extract ceg words = "abcdefghi"
Training goal
Use of slicing strings
Training tips
1. The slicing syntax: [start:end:step] 2. The selected interval starts from the "start" bit and ends at the bit before the "end" bit (not including the end bit itself), 3. Step length Indicates the selection interval, the default step size is positive, that is, select from left to right, if the step size is negative, select from right to left
Reference plan
1. Use slice to intercept, start position is -7, end position is -1 2, reverse selection, step size is 2
Steps
-
The start position is -7, the end position is -1, and the step size is 2
Reference answer
a = "abcdefghi"
b = a[-7:-1:2]
print(b)
Topic 4 [Strengthening training]
Question stem
James has a project about crawlers. He needs to search for the keyword python in a string. Currently he searches through the index() function. Although it can meet the search requirements, he will always report an error when the keyword is not found. , Why is there an error and how to optimize?
Training goal
-
Understand the difference between find function and index function
Training tips
-
The find function returns the index value if it is found, or -1 if it is not found
-
The index function returns the index value if it is found, and reports an error if it cannot be found
Reference plan
-
Replace index by using the find function
Steps
-
Replace index by using the find function
Reference answer
只需要使用find函数替换掉index函数即可，在功能上, find函数index函数完全一致,不同的是index函数在没有查找到关键字的情况下会报ValueError的异常,因此在一般开发环境下通常都会使用find函数
Topic 5 [Strengthening training]
Question stem
1. Determine whether the word great is in the string words. If it is, add an s after each great. If it is not, output that great is not in the string. 2. Change every word in the entire string to lowercase. And make the first letter of each word into capital 3, remove the blank at the beginning and end, and output the processed string
words = " great craTes Create great craters, But great craters Create great craters "
Training goal
-
String related operations
Training tips
-
String related operations to solve the above problems
-
Use judgment sentences to judge the conditions for the validity
Reference plan
-
Use in to determine whether a certain substring is in the parent string
-
Use the replace function to replace the substring
-
Use the lower function to change the string to lowercase
-
Use the title function to capitalize the first letter of a word
-
Use the strip function to remove whitespace at the beginning and end of a string
Steps
-
Use in to determine whether a certain substring is in the parent string
-
Use the replace function to replace the substring
-
Use the lower function to change the string to lowercase
-
Use the title function to capitalize the first letter of a word
-
Use the strip function to remove whitespace at the beginning and end of a string
Reference answer
words = " great craTes Create great craters, But great craters Create great craters "
# 判断单词great是否在这个字符串中
if 'great' in words:
# 将每一个great替换成greats
words = words.replace("great", "greats")
# 将单词变成小写
words = words.lower()
# 将每一个单词的首字母都大写
words = words.title()
# 去除首尾的空白
words = words.strip()
# 最后进行输出
print(words)
else:
print("great不在该字符串中")2. List
Topic 1 [Strengthening training]
Question stem
There is a list, judge whether each element in the list ends with s or e, if it is, put it into a new list, and finally output the new list
list = ["red", "apples", "orange", "pink", "bananas", "blue", "black", "white"]Training goal
Let students know the loop and value acquisition of the list, as well as the operation method of the list
Training tips
-
How to find every element in the list?
-
How to determine what character the elements in the list end with?
Reference plan
-
Use a loop to get every element in the list?
-
The elements in the list are strings, so you can use the subscript [-1] to get the value of the last character, and then judge.
Steps
-
Traverse each element in the list
-
if determines whether the last character is
sore -
If it is, use the append() method to append the data to the new list.
Reference answer
my_list = ["red", "apples", "orange", "pink", "bananas", "blue", "black", "white"]
# 用来存放以e或者s结尾的字符串
new_list = []
for i in my_list:
# 判断列表中每一个元素是否以s或e结尾
if i[-1] == 's' or i[-1] == 'e':
new_list.append(i)
# 打印出这个新的列表
print(new_list)Method Two:
Use the method in the string to judge.
my_list = ["red", "apples", "orange", "pink", "bananas", "blue", "black", "white"]
# 用来存放以e或者s结尾的字符串
new_list = []
for i in my_list:
# 判断列表中每一个元素是否以s或e结尾
if i.endswith('s') or i.endswith('e'):
new_list.append(i)
# 打印出这个新的列表
print(new_list)
Topic 2 [Strengthening training]
Question stem
Given a list, first delete the element starting with s, after deleting, modify the first element to "joke", and make a copy of the last element and place it after joke
my_list = ["spring", "look", "strange", "curious", "black", "hope"]Training goal
List related operations
Training tips
-
Traverse the list through the for loop to get each element
-
Modify the list through the operation method of the list
Reference plan
-
Get each element through the for loop
-
Remove the elements in the list by remove
-
Insert an element at the specified position through the insert function
Steps
-
Get each element through the for loop to determine whether it
sstarts with -
If the condition is true, delete the selected element through remove
-
Get the last element, place the element at the specified position by replace
Reference answer
my_list = ["spring", "look", "strange" "curious", "black", "hope"]
for i in my_list[:]:
# 删除以s开头的元素，
if i[0] == 's':
my_list.remove(i)
# 修改第一个元素为"joke"
my_list[0] = "joker"
# 获取最后一个元素
last_one = my_list[-1]
# 将最后一个元素放在joke的后面
my_list.insert(1, last_one)
print(my_list)
Topic 3 [Strengthening training]
Question stem
Combine the following two lists, de-duplicate the combined list, and output in descending order
list1 = [11, 4, 45, 34, 51, 90]
list2 = [4, 16, 23, 51, 0]
Training goal
Use of List Operation Method
Training tips
-
How to merge two lists?
-
How to remove duplicate lists?
-
How to sort and output in descending order?
Reference plan
-
To merge lists, you can use the extend() method or add two lists.
-
There are two options for list deduplication
-
Implement the method yourself, with the help of a new list, loop through the original list to determine whether the element is in the new list, if it is, traverse the next element, if not, add it to the new list.
-
Use set() to remove duplicates
-
The sort function can realize sorting, and the parameter reverse=True sorts the list in reverse order
Steps
1. Use + to splice the list (or use extend) 2. List to remove duplicates 3. Use the sort function with parameter reverse=True to sort the list in reverse order
Reference answer
plan 1
list1 = [11, 4, 45, 34, 51, 90]
list2 = [4, 16, 23, 51, 0]
# 1. 使用 + 合并两个列表
my_list = list1 + list2
# 2. 列表去重
# 2.1 定义新的空列表保存去重后的数据
my_list1 = []
# 2.2 遍历合并后的列表
for i in my_list:
# 2.3 判断i 是否在my_list1 中
if i in my_list1:
# 2.3.1 如果存在,直接下一次循环
continue
else:
# 2.3.2 将i添加到my_list1 中.
my_list1.append(i)
# 3. 循环结束,得到去重后的列表 my_list1,进行排序
my_list1.sort(reverse=True)
# 4. 输出最后的结果
print(my_list1)
Option 2 Don't worry about it for now and learn later
Use set, de-duplication,
set is also a container, with automatic de-duplication function (will learn later)
Just need to understand for now.
list1 = [11, 4, 45, 34, 51, 90]
list2 = [4, 16, 23, 51, 0]
# 列表拼接
list3 = list1 + list2
# 列表去重
list4 = set(list3)
list5 = list(list4)
# 列表降序输出
list5.sort(reverse=True)
print(list5)3. Tuple
Topic 1 [Strengthening training]
Question stem
There are two lines of code as follows: tuple1 = (2) tuple2 = (2,) What is the difference between tuple1 and tuple2
Training goal
Define a tuple of elements
Training tips
What can be seen by the naked eye is only a comma difference, so how does he understand it in python?
Reference plan
Use the type() method to distinguish these two variables separately
Steps
Use type(tuple1) to compare with the result of type(tuple12)
Reference answer
tuple1 = (2)
tuple2 = (2,)
print(type(tuple1))
print(type(tuple2))
# 对于tuple1 = （2），python解释器会将小括号理解成一个运算符号，那么这时候 返回的值是一个int类型
# 所以对于只有一个元素的元组来说，要创建一个元组，那么就必须要加逗号
Topic 2 [Strengthening training]
Question stem
There is the following code, please answer the question?
my_tuple = ("itcast", "python", "CPP", 18, 3.14, True)-
Use the subscript method to output the elements in the tuple
"CPP" -
Use for loop to traverse tuples
-
Use while loop to iterate through tuples
Training goal
-
Subscript operations on tuples
-
For loop traversal of tuples
-
While loop traversal of tuples
Training tips
-
Does the subscript in python start from 0 or 1?
-
How to traverse for?
-
How to traverse while? How to write the condition of while?
Reference plan
-
The subscript starts from 0, so the subscript of CPP is 2
-
Use
for ... in ...traversal -
while loop, requires the use of subscripts, conditions can be determined by means
len()implemented
Steps
-
Use the subscript method to take the value of CPP
-
for loop traversal
-
while loop traversal
Reference answer
my_tuple = ("itcast", "python", "CPP", 18, 3.14, True)
# 1. 使用下标的方法，输出元组中的元素 `"CPP"`使用下标的方法，
result = my_tuple[2]
print(result)
# 2. 使用 for 循环遍历元组
for i in my_tuple:
print(i)
print("-" * 20)
# 3. 使用 while 循环遍历元组
i = 0
while i < len(my_tuple):
print(my_tuple[i])
i += 1