Python学习之基础知识

1. 格式化输出

 user_1='韩梅梅'
 user_2='李雷'
 print('{}对{}说："hello"'.format(user_1,user_2))

控制台输出： 

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
韩梅梅对李雷说："hello"

Process finished with exit code 0

---

 f-string

(python3出现的)

user_1='韩梅梅'
user_2='李雷'
print(f'{user_1}对{user_2}说：hello"')

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
韩梅梅对李雷说：hello"

Process finished with exit code 0

---

2. +

连接多个字符串

print("are "+" you"+" ok")

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
are  you ok

Process finished with exit code 0

---

3.列表

my_list=[1,2,'a',1.3]
print(my_list[-4])

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
1

Process finished with exit code 0

---

切片

my_list=[1,2,'a',1.3]


print(my_list[1:3])
print(my_list[1:5:2])
print(my_list[:])
print(my_list[1:])      

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
[2, 'a']
[2, 1.3]
[1, 2, 'a', 1.3]
[2, 'a', 1.3]

Process finished with exit code 0

---

append

追加到后面

my_list=[1,2,'a',1.3]
my_list.append(111)
print(my_list)

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
[1, 2, 'a', 1.3, 111]

Process finished with exit code 0

---

insert

插入

my_list=[1,2,'a',1.3]

my_list.insert(1,'python')
print(my_list)

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
[1, 'python', 2, 'a', 1.3]

Process finished with exit code 0

---

extend

接一个序列，字符串是一个序列

my_list=[1,2,'a',1.3]
my_list.extend('python')
my_list.extend([22,33,44])
print(my_list)

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
[1, 2, 'a', 1.3, 'p', 'y', 't', 'h', 'o', 'n', 22, 33, 44]

Process finished with exit code 0

---

pop()

移除一个元素

my_list=[1,2,'a',1.3]
my_list.pop(1)
print(my_list)

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
[1, 'a', 1.3]

Process finished with exit code 0

---

remove

删除一个元素

my_list=[1,2,'a',1.3]
my_list.remove('a')
print(my_list)

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
[1, 2, 1.3]

Process finished with exit code 0

---

列表的修改

my_list=[1,2,'a',1.3]
my_list[2]=33
print(my_list)

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
[1, 2, 33, 1.3]

Process finished with exit code 0

---

4.元组

（不可变的列表）

my_list=(1,2,'a',1.3)
my_list[2]=33   

print(my_list)

控制台输出：（不可修改的）

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
Traceback (most recent call last):
  File "D:/pythoncode/1.py", line 51, in <module>
    my_list[2]=33   
TypeError: 'tuple' object does not support item assignment

Process finished with exit code 1

其他操作跟列表相同

---

 5.字典

{}：键值对 键--->值

user={
    'name':'Tom'
}

print(user)  

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
{'name': 'Tom'}

Process finished with exit code 0

---

user={
    'name':'Tom',
    'age':18,
    'gender':'male'
}

print(user)
print(user['age'])
print(user['name']) 

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
{'name': 'Tom', 'age': 18, 'gender': 'male'}
18
Tom

Process finished with exit code 0

---

修改

user={
    'name':'Tom',
    'age':18,
    'gender':'male'
}

# 修改
user['age']=20
print(user)

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
{'name': 'Tom', 'age': 20, 'gender': 'male'}

Process finished with exit code 0

---

增加

user={
    'name':'Tom',
    'age':18,
    'gender':'male'
}

# 增加
user['fav']='打篮球'
print(user)

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
{'name': 'Tom', 'age': 18, 'gender': 'male', 'fav': '打篮球'}

Process finished with exit code 0

---

6.函数

作用：

 1.降低编程难度
 2.增加代码复用

# 1+2+3+...100
n=1
s=0
while n<=100:
    s+=n
    n+=1
print(s)

 控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
5050

Process finished with exit code 0

---

现在用函数代替

def qiu_he(n,m):
    s=0
    while n<=m:
        s+=n
        n+=1
    return s

print(qiu_he(1,100))
print(qiu_he(1,50))    

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
5050
1275

Process finished with exit code 0

---

7.文件操作

读文件

f=open('a.txt',encoding='utf-8')
s=f.read()
print(s)

f.close()

a.txt

床前明月光
疑是地上霜
举头望明月
低头思故乡

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py
床前明月光
疑是地上霜
举头望明月
低头思故乡

Process finished with exit code 0

---

写入文件

f=open('b.txt',mode='w',encoding='utf-8')
f.write('我想要个\n')
f.write('女朋友\n')
f.close()

控制台输出：

D:\pythoncode\venv\Scripts\python.exe D:/pythoncode/1.py

Process finished with exit code 0

b.txt

我想要个
女朋友

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