检查Python中是否存在文件

An ability to check if the file exists or not, is very crucial in any application. Often, the applications perform verifications like,

在任何应用程序中&＃xff0c;检查文件是否存在的能力至关重要。 通常&＃xff0c;应用程序会执行验证&＃xff0c;例如&＃xff0c;

• Check if the file exists before appending/writing to it.

  在追加/写入文件之前检查文件是否存在。

• Check if the file exists before reading it.

  在读取文件之前&＃xff0c;请检查文件是否存在。

The python programming language provides multiple methods to check if the file exists or not. The module which provides the functions as ‘os&＃39; , so it is important to import os, while there is a verification on file&＃39;s existence.

python编程语言提供了多种方法来检查文件是否存在 。 提供功能为&＃39;os&＃39;的模块&＃xff0c;因此在验证文件是否存在的同时导入os非常重要。

os.path.exists() (os.path.exists())

-bash-4.2$ ls
python_samples test.txt
-bash-4.2$ python3
Python 3.6.8 (default, Apr 25 2019, 21:02:35)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> from os import path
>>> print(path.exists(&＃39;test.txt&＃39;))
True
>>> print(path.exists(&＃39;test1.txt&＃39;))
False
>>>


os.path.isfile() (os.path.isfile())

-bash-4.2$ ls
python_samples test.txt
-bash-4.2$ python3
Python 3.6.8 (default, Apr 25 2019, 21:02:35)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> print(os.path.isfile(&＃39;test.txt&＃39;))
True
>>> print(os.path.isfile(&＃39;test1.txt&＃39;))
False


The functions, demonstrated above are also available in a lower version of python (<3). However, python version 3.4 provides a function pathlibPath.exists() which is imported from pathlib module for handling the file system path. It uses an object-oriented approach to verify if the file exists or not.

上面演示的功能在较低版本的python(<3)中也可用。 但是&＃xff0c;python 3.4提供了一个函数pathlibPath.exists() &＃xff0c;该函数是从pathlib模块导入的&＃xff0c;用于处理文件系统路径。 它使用一种面向对象的方法来验证文件是否存在。

-bash-4.2$ ls
python_samples test.txt
-bash-4.2$ python3
Python 3.6.8 (default, Apr 25 2019, 21:02:35)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pathlib
>>> test_file &＃61; &＃39;test.txt&＃39;
#create a file object
>>> file &＃61; pathlib.Path(test_file)
>>> if file.exists():
... print("file {} exists".format(test_file))
... else:
... print("file {} does not exists".format(test_file))
...
file test.txt exists


-bash-4.2$ ls
python_samples test.txt
-bash-4.2$ python3
Python 3.6.8 (default, Apr 25 2019, 21:02:35)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pathlib
>>> test_file &＃61; &＃39;test1.txt&＃39;
>>> file &＃61; pathlib.Path(test_file)
>>> if file.exists():
... print("file {} exists".format(test_file))
... else:
... print("file {} does not exists".format(test_file))
...
file test1.txt does not exists
>>>


简而言之 (In a nutshell)

• Use path.exists to verify if the given file exists.

  使用path.exists验证给定文件是否存在。

• Use path.isfile to check whether a path is file.

  使用path.isfile来检查路径是否为文件。

• The version Python 3.4 and above provides a pathlib Module to verify the existence of file.

  Python 3.4及更高版本提供了一个pathlib模块来验证文件是否存在。

Along with the above-mentioned methods, there is another straight forward pythonic way for checking the existence of the file. Use the open() method to open the file.

除了上述方法外&＃xff0c;还有另一种简单的Python方式可以检查文件的存在。 使用open()方法打开文件。

-bash-4.2$ ls
python_samples test.txt
-bash-4.2$ python3
Python 3.6.8 (default, Apr 25 2019, 21:02:35)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> try:
... open(&＃39;text.txt&＃39;)
... except:
... print("file does not exists")
...
file does not exists


-bash-4.2$ ls
python_samples test.txt
-bash-4.2$ python3
Python 3.6.8 (default, Apr 25 2019, 21:02:35)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> file_name &＃61; &＃39;test.txt&＃39;
>>> try:
... with open(file_name) as f:
... print("{} exists".format(file_name))
... except:
... print("{} does not exists".format(file_name))
...
test.txt exists
>>>


Usage of with in above example, ensures the file is closed after the file operation.

在上面的示例中使用with可以确保在文件操作后关闭文件。

翻译自: https://www.includehelp.com/python/check-if-a-file-exists.aspx