检查Python中是否存在文件

雨点打透心脏的1/2处 2023-03-05 09:59 35阅读 0赞

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，检查文件是否存在的能力至关重要。 通常，应用程序会执行验证，例如，

*  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，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' , so it is important to import os, while there is a verification on file'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'os'的模块，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('test.txt'))
    True
    >>> print(path.exists('test1.txt'))
    False
    >>>

### os.path.isfile() **(**os.path.isfile()**)** ###

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，python 3.4提供了一个函数**pathlibPath.exists()** ，该函数是从**pathlib模块**导入的，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 = 'test.txt'
    #create a file object
    >>> file = 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 = 'test1.txt'
    >>> file = 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，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('text.txt')
    ... 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 = 'test.txt'
    >>> 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][https_www.includehelp.com_python_check-if-a-file-exists.aspx]

[https_www.includehelp.com_python_check-if-a-file-exists.aspx]: https://www.includehelp.com/python/check-if-a-file-exists.aspx