python进阶(7)–文件与异常
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1、with语句
#采用idea的sources root的相对路径
with open('..//data//pi_digits.txt') as file_object:
contents = file_object.read()
#打印同时剔除空行
print(contents.rstrip())
查看结果：
3.1415926535
8979323846
2643383279
2、绝对路径
file_path='D:/Users/Mr.White/PycharmProjects/pythonProject/data/pi_digits.txt'
with open(file_path) as file_object:
contents = file_object.read()
print(contents.rstrip())
查看结果：
3.1415926535
8979323846
2643383279
3、for循环逐行读取
with open('../data/pi_digits.txt') as file_object:
for line in file_object:
print(line.rstrip())
查看结果：
3.1415926535
8979323846
2643383279
4、readline()方法，将文件的内容存储在列表内
with open('../data/pi_digits.txt') as file_object:
lines=file_object.readlines()
for line in lines:
print(line.rstrip())
查看结果：
3.1415926535
8979323846
2643383279
优化代码，拼接字符串读取
with open('../data/pi_digits.txt') as file_object:
lines=file_object.readlines()
pi_string=''
for line in lines:
pi_string+=line.strip()
print(pi_string)
print(len(pi_string))
查看结果：
3.141592653589793238462643383279
32
1、with，覆盖模式
file_name='../data/programming.txt'
with open(file_name,'w') as file_object:
file_object.write("I love programming.")
查看文件(../data/programming.txt)：
I love programming.
2、写入多行
file_name='../data/programming.txt'
with open(file_name,'w') as file_object:
file_object.write("I love programming.\n")
file_object.write("i love creating new games.\n")
查看文件(../data/programming.txt)：
I love programming.
i love creating new games.
3、with，附加模式
with open(file_name,'a') as file_object:
file_object.write("I also love fing...\n")
file_object.write("i love creating apps that...\n")
查看文件(../data/programming.txt)：
I love programming.
i love creating new games.
I also love fing...
i love creating apps that...
1、解决异常(ZeroDivisionError)：try except
try:
print(5/0)
except ZeroDivisionError:
print("You can't divide by zero!")
查看结果：
You can't divide by zero!
2、解决异常(FileNotFoundError):try except
filename="testfile.txt"
try:
with open(filename,encoding='utf-8') as f:
contents=f.read()
except FileNotFoundError:
print(f"sorry,the file {filename} does not exits.")
查看结果：
sorry,the file testfile.txt does not exits.
3、异常时静默处理：pass
try:
print(5/0)
except ZeroDivisionError:
pass
无显示结果
1、写入数据
import json
number=[2,3,5,7,11,13]
filename='../data/number.json'
with open(filename,'w') as f:
json.dump(number,f)
查看结果(number.json)
[2, 3, 5, 7, 11, 13]
2、读取数据
filename='../data/number.json'
with open(filename) as f:
numbers=json.load(f)
print(numbers)
查看结果：
[2, 3, 5, 7, 11, 13]
3、json+input：保存和读取用户输入
username=input("What is your name?")
filename='username.json'
with open(filename,'w') as f:
json.dump(username,f)
print(f"We'll remember you when you come back,{username}!")
with open(filename) as f:
username=json.load(f)
print(f"Welcom back,{username}")
查看结果：
What is your name?mike
We'll remember you when you come back,mike!
Welcom back,mike
4、封装用户输入与存储
def get_stored_username():
"""当没有错误时读取保存的用户名"""
filename='username.json'
try:
with open(filename) as f:
username=json.load(f)
except FileNotFoundError:
return None
else:
return username
def get_new_username():
"""验证新用户名"""
username=input("What is your name?")
filename='username.json'
with open(filename,'w') as f:
json.dump(username,f)
return username
def greet_user():
"""greet the user by name"""
username=get_stored_username()
if username:
print(f"Welcome back,{username}!")
else:
username=get_new_username()
print(f"We will remember you when you come back,{username}!")
greet_user()
查看运行结果：
Welcome back,mike!
