How do I check whether a file exists without exceptions?

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北海茫月
北海茫月 2020-11-21 05:07

How do I check if a file exists or not, without using the try statement?

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  • 2020-11-21 05:16

    Check file or directory exists

    You can follow these three ways:

    Note1: The os.path.isfile used only for files

    import os.path
    os.path.isfile(filename) # True if file exists
    os.path.isfile(dirname) # False if directory exists
    

    Note2: The os.path.exists used for both files and directories

    import os.path
    os.path.exists(filename) # True if file exists
    os.path.exists(dirname) #True if directory exists
    

    The pathlib.Path method (included in Python 3+, installable with pip for Python 2)

    from pathlib import Path
    Path(filename).exists()
    
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  • 2020-11-21 05:17
    import os.path
    
    def isReadableFile(file_path, file_name):
        full_path = file_path + "/" + file_name
        try:
            if not os.path.exists(file_path):
                print "File path is invalid."
                return False
            elif not os.path.isfile(full_path):
                print "File does not exist."
                return False
            elif not os.access(full_path, os.R_OK):
                print "File cannot be read."
                return False
            else:
                print "File can be read."
                return True
        except IOError as ex:
            print "I/O error({0}): {1}".format(ex.errno, ex.strerror)
        except Error as ex:
            print "Error({0}): {1}".format(ex.errno, ex.strerror)
        return False
    #------------------------------------------------------
    
    path = "/usr/khaled/documents/puzzles"
    fileName = "puzzle_1.txt"
    
    isReadableFile(path, fileName)
    
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  • 2020-11-21 05:20

    How do I check whether a file exists, without using the try statement?

    In 2016, this is still arguably the easiest way to check if both a file exists and if it is a file:

    import os
    os.path.isfile('./file.txt')    # Returns True if exists, else False
    

    isfile is actually just a helper method that internally uses os.stat and stat.S_ISREG(mode) underneath. This os.stat is a lower-level method that will provide you with detailed information about files, directories, sockets, buffers, and more. More about os.stat here

    Note: However, this approach will not lock the file in any way and therefore your code can become vulnerable to "time of check to time of use" (TOCTTOU) bugs.

    So raising exceptions is considered to be an acceptable, and Pythonic, approach for flow control in your program. And one should consider handling missing files with IOErrors, rather than if statements (just an advice).

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  • 2020-11-21 05:23

    If you imported NumPy already for other purposes then there is no need to import other libraries like pathlib, os, paths, etc.

    import numpy as np
    np.DataSource().exists("path/to/your/file")
    

    This will return true or false based on its existence.

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  • 2020-11-21 05:26

    In 2016 the best way is still using os.path.isfile:

    >>> os.path.isfile('/path/to/some/file.txt')
    

    Or in Python 3 you can use pathlib:

    import pathlib
    path = pathlib.Path('/path/to/some/file.txt')
    if path.is_file():
        ...
    
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  • 2020-11-21 05:26

    You could try this (safer):

    try:
        # http://effbot.org/zone/python-with-statement.htm
        # 'with' is safer to open a file
        with open('whatever.txt') as fh:
            # Do something with 'fh'
    except IOError as e:
        print("({})".format(e))
    

    The ouput would be:

    ([Errno 2] No such file or directory: 'whatever.txt')

    Then, depending on the result, your program can just keep running from there or you can code to stop it if you want.

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