输入输出

输入

## 回文测试
def reverse(text):
    return text[::-1]


def is_palindrome(text):
    return text == reverse(text)


something = input("Enter text: ")
if is_palindrome(something):
    print("Yes, it is a palindrome")
else:
    print("No, it is not a palindrome")

1. [::-1], 倒序反转字符串

文件写

poem ="""
    早发白帝城
     唐 李白
朝辞白帝彩云间，千里江陵一日还。
两岸猿声啼不住，轻舟已过万重山。 
"""
f = open('poem.txt', 'w',encoding='utf-8')

f.write(poem)
f.close()

1. f = open('poem.txt', 'w',encoding='utf-8'), 文件写
2. f.write(poem), 文件写入内容

文件输出

f = open('poem.txt', 'r', encoding='utf-8')

while True:
    line = f.readline()
    ## 文件结束
    if len(line) == 0:
        break
    ## readline 已经有换行符
    print(line, end='')

f.close()

1. f = open('poem.txt', 'r', encoding='utf-8'), 文件读
2. line = f.readline(), 文件一行行读

with

with open('poem.txt', 'r', encoding='utf-8') as f:
    while True:
        line = f.readline()
        if len(line) == 0:
            break
        print(line.strip())

1. with open('poem.txt', 'r', encoding='utf-8') as f:, 语法糖写法， 可不容易出错

StringIO

在内存中读写Str

读

from io import StringIO
f = StringIO()
f.write('hello')
f.write(' ')
f.write('world!')
print(f.getvalue())

1. f = StringIO(), f.write(str)， 像文件一样写入str
2. f.getvalue(), 获得写入的str

写

from io import StringIO
f1 = StringIO('Hello!\nHi\nGoodbye!\n')
while True:
    s = f1.readline()
    if s == '':
        break
    print(s.strip())

1. f1 = StringIO('Hello!\nHi\nGoodbye!\n'),用一个str 初始化 StringIO,
2. s = f1.readline(),像文件一样读取

持久化

import pickle

shoplistfile = 'shoplist.data'

shoplist  = ['apple', 'mango', 'carrot']

f = open(shoplistfile, 'wb')
## 转储对象至文件
pickle.dump(shoplist, f)

f.close()

f = open(shoplistfile, 'rb')
## 从文件中载入对象
storeList = pickle.load(f)

print(storeList)