Hello Python

本博客主要用来记录python的学习笔记

入坑

a,b=input().split()
print(int(a)+int(b))

print("Hello Python!")

format和%

Python中%s、%d、%f意义及用法详解
Python format 格式化函数

a=1/3
print("%.3f"%(a))
url="xxxxxxxxxxxxx"
payload="cccccccccc"
print("website:{}; payload:{}".format(url,payload))

lstrip和rstrip和strip

'''
>>> a = '       welcome come to Beijing           '
>>> a.strip()
'welcome come to Beijing'
>>> a.rstrip()
'       welcome come to Beijing'
>>> a.lstrip()
'welcome come to Beijing           '
'''
a = '       welcome come to Beijing           \n'
print(a)
print(a.strip())

python的函数可以很方便的进行传列表的操作，并且代码非常简明易懂

python的文件操作

文件名xiangao.txt
文件内容：

We must Study Python to make this world a better place!
Why is Xiangao so strong,
I can't imagine!

测试程序1：

with open('xiangao.txt') as file_object:
    print(file_object.read())

测试结果：

We must Study Python to make this world a better place!
Why is Xiangao so strong,
I can't imagine!

测试程序2：逐行读取

with open('xiangao.txt') as file_object:
    for object in file_object:
        print(object)

测试结果：

We must Study Python to make this world a better place!

Why is Xiangao so strong,

I can't imagine!

Process finished with exit code 0

测试程序3：逐行读取，消回车

with open('xiangao.txt') as file_object:
    for object in file_object:
        print(object.strip())

We must Study Python to make this world a better place!
Why is Xiangao so strong,
I can't imagine!

测试程序4：逐行读取并存储

with open('xiangao.txt') as file_object:
    object=file_object.readlines()
    for i in object:
        print(i)

测试结果：

We must Study Python to make this world a better place!

Why is Xiangao so strong,

I can't imagine!

当我们需要进行写入文件操作时，调用open时必须提供另外一个参数，第一个参数文件的路径，第二个参数是'w'告诉Python我要进行写入操作，如果不加参数默认就是只读模式，还有附加模式'a'，可读可写模式'r+'
测试程序：

with open('xiangao.txt','r+') as file_object:
    # file_object.write('\nI must be his friend!')
    object=file_object.readlines()
    for i in object:
        print(i)

这里出现了一些奇怪的小问题，但是我觉得无伤大雅。

try_except：

Python使用被称为异常的特殊对象来管理程序执行期间发生的错误。每当发生让Python不知所措的错误时，他都会创建一个异常对象。如果你编写了处理该异常的代码，程序将继续运行：如果你未对异常进行处理，程序将停止，并显示一个traceback，其中包含有关异常的报告。异常是使用try-except代码块进行处理的。try-except代码块让Python执行指定的操作，同时告诉Python发生异常时怎么办。使用try-except代码块，即使出现异常，程序也将继续运行，显示你编写的友好的错误消息，而不是令用户迷惑的traceback。
举个例子：

a,b=input().split()
a=int(a)
b=int(b)
print(a/b)

这是一个除法计算器：
但如果我们输入一个除数为0，则程序会报错：

Traceback (most recent call last):
  File "D:\njc\SAFETY WEB\Python学习\try_except.py", line 4, in <module>
    print(a/b)
ZeroDivisionError: division by zero

这时就需要使用try except模块了

a,b=input().split()
a=int(a)
b=int(b)
try:
    c=a/b
except:
    print("0 is not allowed");
else:
    print(c)

else中放的是当try中代码块执行成功后的后续执行操作
也可以这么写：

a,b=input().split()
a=int(a)
b=int(b)
try:
    c=a/b
except ZeroDivisionError:
    print("0 is not allowed");
else:
    print(c)

运行结果：

D:\venv\Scripts\python.exe "D:/njc/SAFETY WEB/Python学习/try_except.py"
5 0
0 is not allowed

Process finished with exit code 0

D:\venv\Scripts\python.exe "D:/njc/SAFETY WEB/Python学习/try_except.py"
5 1
5.0

Process finished with exit code 0