"Python Programming Quick Start" Part 8: Understanding Python's reading and writing files

xiaolinen

"Python Programming Quick Start" Part 8: Understanding Python's reading and writing files [Copy link]

1. Some basic knowledge

1.1, What are absolute paths and relative paths?

"Absolute path", always starts from the root folder.

"Relative path", relative to the program's current working directory.

1.2, Verify the effectiveness of the path

If the path exists, calling the exists() method returns True, otherwise it returns False;

If the path exists and is a file, calling the is_file() method returns True, otherwise it returns False;

If the path exists and is a folder, calling the is_dir() method returns True, otherwise it returns False;

The operation examples are as follows:

"""
    绝对路径和相对路径
"""

from pathlib import Path

# 验证路径是否存在
a = Path('D:/PyCharm')
print(a.exists())

# 验证路径是否存在，并是一个文件
b = Path('D:/PyCharm/project/pythonProject/test/python_test.py')
print(b.is_file())

# 验证路径是否存在，并是一个文件夹
c = Path('D:/PyCharm/project/pythonProject/test')
print(c.is_dir())


#结果如下
#True
#True
#True

2: Read and write files

In Python, reading and writing files is a 3-step process:

2.1, call the open() function and return a File object.

2.2, call the read() or write() method of the File object.

3.3, Call the close() method of the File object to close the file.

The operation examples are as follows:

"""
    文件写入和读出操作
"""
# 打开文件 w 写入，文件如果不存在，会自动创建
f = open("E:/Project/python/文件.txt", "w", encoding="UTF-8")

# write方法写入，内容是写入内存缓存区
f.write("学python，不后悔！")

# flush刷新，写入到磁盘
f.flush()

# close关闭文件IO
f.close()

# 打开文件 r 只读模式 要求文件必须存在
f = open("E:/Project/python/文件.txt", "r", encoding="UTF-8")

# read方法读出
a = f.read(12)
print("a =", a)

# close关闭文件IO
f.close()


#结果如下
#a = 学python，不后悔！

lugl4313820

f.flush is very important, otherwise writing may fail sometimes.

xiaolinen

lugl4313820 posted on 2024-5-20 07:00 f.flush is very important, otherwise sometimes you may not be able to write successfully.

Indeed. Boss, please give me more advice!

hellokitty_bean

By the way, the current Python version does not distinguish between OS path slashes? I just tried it and it passed.

Indeed. Dear two masters, please give me more advice!

xiaolinen

hellokitty_bean posted on 2024-5-20 10:29 By the way, the current Python version does not distinguish between OS path slashes? I just tried it, Pass. Indeed. Two masters, please give me more advice!

Learn together and make progress together

xiaolinen

#Additional mode writes data, and the operation is supplemented as follows:

# Open file a in append mode and write to the file. If the file does not exist, it will be created automatically.

f = open("E:/Project/python/file.txt", "a", encoding="UTF-8")



# The write method writes the content to the memory buffer

f.write("\n123456")



# flush refresh, write to disk

f.flush()



# close closes the file IO

f.close()



# Open the file r read-only mode requires the file to exist

f = open("E:/Project/python/file.txt", "r", encoding="UTF-8")



# read method reads out

a = f.read(19)

print("a =", a)



# close closes the file IO

f.close()