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 02. +
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 04.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
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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