读取整个文件

with open('data.txt') as file_object:
    contents = file_object.read()
print(contents)
print(contents.rstrip()) #删除字符串末尾空白

文件路径

with open('text_files//data.txt') as file_object:

file_path = '/home/eh/data.txy'
with open(file_path) as file_object:

逐行读取

with open(file_path) as file_object:
    for line in file_path:
        print(line.rstrip())

创建一个包含

文件各行内容的列表

filename ='data.txt'
with open(filename) as file_object:
    lines = file_object.readlines()
for line in lines:
    print(line.rstrip())

使用文件内容

data_string = ''
for line in lines:
    data_string += line.rstrip() #循环加入data_string
print(data_string)

打印圆周率小数点后10位数

3.1415926535…

print(f"{data_string[:12]}…")

数列中是否包含这个字段

……

my_data = input("输入数字,字符串是否有这个数：")
if my_data in data_string:
    print("你的数字在这个字符串中")
else:
    print("你的数字不在这个字符串中")

写入空文件

file = 'abc.txt'
with open(file) as file_object:
    file_object.write("我是一个蘑菇。")

写入多行open(file, 'w')

with open(file, 'w') as file_object:
    file_object.write("我是一个蘑菇。\n")
    file_object.write("我不是一个蘑菇。\n")

附加到文件open(file, 'a')

with open(file, 'a') as file_object:
    file_object.write("我是一个蘑菇。\n")

json.dump()

可以接受两个实参

import json

number =[2,3,5]
filename = 'number.json'
with open(filename, 'w') as f:
    json.dump(number, f)

number.json文件中：

[2, 3, 5]

json.load()

将列表

读取到内存中

with open(filename, 'w') as f:
    numbers = json.load(f)
print(numbers)

代码

输出

username.json文件

存储用户

import json

username = input("你的名字：")
filename = 'username.json'
with open(filename, 'w') as f:
    json.dump(username, f)
    print(f"Hello,{username}!")

你的名字：Ann

Hello,Ann!

"Ann"

向已存储的用户

发出问候

import json
filename = 'username.json'
with open(filename) as f:
    username = json.load(f)
    print(f"欢迎回来，{username}!")

欢迎回来，Ann!

如用户已存储，加载他。如果没有，则提示用户输入并存储。

import json

filename = 'username.json'
try:
    with open(filename) as f:    #尝试打开username.json
        username = json.load(f)    #如果username.json存在
except FileNotFoundError:    #username.json不存在
    username = input("你的名字：")
    with open(username, 'w') as f:
        json.dump(username, f)    #存储
        print(f"Hello,{username}!")
else:
    print(f"欢迎回来，{username}!")