Python Programming for Beginners: A Step-by-Step Guide to Learn one of the Most Popular and Easy Programming Languages. Learn Basic Python Coding Fast with Examples and Tips by McKinnon Julian James

Author:McKinnon, Julian James [McKinnon, Julian James]
Language: eng
Format: epub
Published: 2020-02-08T16:00:00+00:00

The first method to handle the FileNotFoundError exception is to make sure that all the common reasons do not cause it.

Once you do, then you will need to choose the best way to handle the error, which is completely dependent on the reason you are opening a file in the first place.

Checking If File Exists

Again, there are always two ways to handle an exception: preventive and reactive.

The preventive method is to check if the file exists in the first place.

To do that, you will need to use the os (os.py) module that comes with your Python installation.

Then, you can use its path module’s isfile() function.

The path module’s file name depends on the operating system (posixpath for UNIX, ntpath for Windows, macpath for old MacOS).

For example:

>>> from os import path

>>> path.isfile("random.txt" )

False

>>> path.isfile("sampleFile.txt")

True

>>> _

Try and Except

You can also do it the hard way by using try, except, and else blocks.

>>> def openFile(filename):

try:

x = open(filename, "r")

except FileNotFoundError:

print("The file '" + filename + "' does not exist."

except FileNotFound:

print("The file '" + filename + "' does exist."

>>> openFile("random.txt")

The file 'random.txt' does not exist.

>>> openFile("sampleFile.txt")

The file 'sampleFile.txt' does exist.

>>> _

Creating a New File

If the file does not exist, and your goal is to overwrite any existing file anyway, then it will be best for you to use the "w" or "w+" access mode.

The access mode creates a new file for you if it does not exist.

For example:

>>> x = open("new.txt", "w")

>>> x.tell()

0

>>> _

If you are going to read and write, use "w+" access mode instead.

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