- 文件读取
- 写入文件
- 异常处理
- 存储数据的实例
1、从文件中读取数据
file_reader.py
with open('./../files/pi_digits.txt') as file_object:
content = file_object.read()
print(content)
open() 打开文件 接受一个参数 要打开的文件名称
close() 关闭文件，python会再合适的时间自动将其关闭
逐行读取
with open('./../files/pi_digits.txt') as file_object:
# content = file_object.read()
# print(content)
# print(content.strip())
for line in file_object:
print(line)
# print(line.strip())
使用 print(line.strip()) 去除空格
使用文件内容 pi_string.py
filename = './../files/pi_digits.txt'
with open(filename) as file_object:
lines = file_object.readlines()
pi_string = ''
for line in lines:
pi_string += line.strip()
print(pi_string)
print(len(pi_string))
strip() 删除空格
rstrip() 删除左边空格
2、写入文件
write_message.py
filename = './../files/programming.txt'
with open(filename, 'w') as file_object:
file_object.write("I love programming")
open() 第一个参数 文件名，
第二个参数 'w' 以写入模式打开这个文件，可指定读取模式('r'), 写入模式('w'), 附件模式('a'), h或读取写入文件的模式('r+')。如果没有指定模式默认只读模式打开文件。
写入多行 并换行
filename = './../files/programming.txt'
with open(filename, 'w') as file_object:
file_object.write("I love programming.\n")
file_object.write("I love creating new games.\n")
3、异常
division.py
print("Give me two numbers, and I`ll divide them.")
print("Enter 'q to quit.")
while True:
first_number = input("\nFirst number: ")
if first_number == 'q':
break
second_number = input("\nSecond number: ")
try:
answer = int(first_number) / int(second_number)
except ZeroDivisionError:
print("You can`t divide by zero!")
else:
print(answer)
try except 避免程序崩溃
else 执行没有异常的代码块
pass 使代码继续执行
4、储存数据
使用json.dupm() 和json.load()
函数json.dump() 接受两个实参 ：要储存的数据以及可用于储存数据的文件对象
将数字串写入文件
number_writer.py
import json
numbers = [2, 3, 5, 7, 11, 13]
filename = './../files/numbers.json'
with open(filename, 'w') as f_obj:
json.dump(numbers, f_obj)
json.load() 加载数据
保存读数用户信息
remember_me.py
import json
# 如果以前储存了用户名，就加载他
# 否则，就提醒用户输入用户名并储存它
filename = './../files/username.json'
try:
with open(filename) as f_obj:
username = json.load(f_obj)
except FileNotFoundError:
username = input("what is your name? ")
with open(filename, 'w') as f_obj:
json.dump(username, f_obj)
print("We`ll remember you when you come back," + username + "!")
else:
print("Welcome back, " + username + "!")
重构其方法，使其更有设计感
import json
# 如果以前储存了用户名，就加载他
# 否则，就提醒用户输入用户名并储存它
def get_stored_username():
"""如果以前储存了用户名，就加载他"""
filename = './../files/username.json'
try:
with open(filename) as f_obj:
username = json.load(f_obj)
except FileNotFoundError:
return None
else:
return username
def get_new_username():
"""提醒用户输入用户名"""
username = input("what is your name? ")
filename = './../files/username.json'
with open(filename, 'w') as f_obj:
json.dump(username, f_obj)
return username
def greet_user():
"""问候用户， 并指出其名字"""
username = get_stored_username()
if username:
print("Welcome back, " + username + "!")
else:
username = get_new_username()
print("We`ll remember you when you come back," + username + "!")
greet_user()
文章参考来源 Eric Matthes [ Python Crash Cource]
2022/09/08 封控于成都期间第八天
