文件

读取文件

# 打开文件
file = open('./txt.txt')

# 读取文件
text = file.read()
print(text)

# 关闭
file.close()

读取文件后文件指针会改变

# 打开文件
file = open('./txt.txt')

# 读取文件
text = file.read()
print(text)
print(len(text))

print('-' * 50)

text2 = file.read()
print(text2)
print(len(text2))

# 关闭
file.close()

写入文件

# 打开
# file = open('./text.txt', 'w')
file = open('./text.txt', 'a')

# 写入文件
file.write('hello world!')

# 关闭文件
file.close()

分行读取文件

file = open('./txt.txt')

while True:
    text = file.readline()

    # 判断是否读取到内容
    if not text:
        break

    print(text)

file.close()

复制文件

# 打开
file_read = open('./txt.txt')
file_write = open('./txt[附件].txt', 'w')


# 读、写
text = file_read.read()
file_write.write(text)


# 关闭
file_read.close()
file_write.close()

""" 复制大文件 """
# 打开
file_read = open('./txt.txt')
file_write = open('./txt[附件].txt', 'w')


# 读、写
while True:
    text = file_read.readline()

    if not text:
        break

    file_write.write(text)


# 关闭
file_read.close()
file_write.close()

eval

input_str = input('输入算术题：')

print(eval(input_str))

import os
print(os.getcwd())  # 获取当前工作目录路径
print(os.path.abspath('.'))  # 获取当前工作目录路径
print(os.path.abspath('txt.txt'))  # 获取当前目录文件下的工作目录路径
print(os.path.abspath('..'))  # 获取当前工作的父目录 ！注意是父目录路径
print(os.path.abspath(os.curdir))  # 获取当前工作目录路径
print(os.listdir())

with

# 自己实现
from contextlib import contextmanager

@contextmanager
def my_open(path, mode):
    f = open(path, mode)
    yield f
    f.close()

with my_open('out.txt', 'w') as f:
    f.write('hello , the simplest context manager')

# with open打开文件
with open('out.txt', 'w') as f:
    f.write('hello , the simplest context manager')

# 上下文管理器
with open('./1.txt', 'wb') as f:
    f.write('hello flask'.encode('utf-8'))


class Foo(object):
    def __enter__(self):
        """ 进入with语句的时候被with调用 """
        print('enter called')

    def __exit__(self, exc_type, exc_val, exc_tb):
        """ 离开with语句的时候被with调用 """
        print('exit called')
        print('exc_type: %s' % exc_type)
        print('exc_val: %s' % exc_val)
        print('exc_tb: %s' % exc_tb)

with Foo() as foo:
    print('hello python')
    a = 1 / 0
    print('hello end')

# 文件

文件