Python Programming Tutorial How to Open and Read in File

Summary: in this tutorial, y'all larn various ways to read text files in Python.

TL;DR

The following shows how to read all texts from the readme.txt file into a cord:

            
                              with                open('readme.txt')                as                f:     lines = f.readlines()            
                          Code language:              JavaScript              (              javascript              )                      

Steps for reading a text file in Python

To read a text file in Python, y'all follow these steps:

• First, open a text file for reading by using the open() part.
• Second, read text from the text file using the file read(), readline(), or readlines() method of the file object.
• Third, close the file using the file close() method.

one) open up() role

The open() office has many parameters only you'll be focusing on the first 2.

            
              open(path_to_file, manner)            
          

The path_to_file parameter specifies the path to the text file.

If the file is in the same folder equally the programme, you just need to specify the name of the file. Otherwise, you need to specify the path to the file.

To specify the path to the file, you use the forward-slash ('/') fifty-fifty if you're working in Windows.

For example, if the file is readme.txt stored in the sample folder every bit the plan, y'all demand to specify the path to the file as c:/sample/readme.txt

The mode is an optional parameter. It's a string that specifies the way in which you want to open the file.

The following table shows bachelor modes for opening a text file:

Style	Description
'r'	Open for text file for reading text
'w'	Open a text file for writing text
'a'	Open a text file for appending text

For case, to open a file whose name is the-zen-of-python.txt stored in the aforementioned folder as the program, you use the post-obit code:

            
                              f = open('the-zen-of-python.txt','r')            
                          Code linguistic communication:              JavaScript              (              javascript              )                      

The open() function returns a file object which you will utilise to read text from a text file.

ii) Reading text methods

The file object provides you lot with three methods for reading text from a text file:

• read() – read all text from a file into a string. This method is useful if you take a modest file and you desire to dispense the whole text of that file.
• readline() – read the text file line by line and return all the lines as strings.
• readlines() – read all the lines of the text file and return them as a list of strings.

iii) close() method

The file that yous open will remain open up until yous close it using the close() method.

It's important to close the file that is no longer in use. If you lot don't close the file, the programme may crash or the file would be corrupted.

The following shows how to call the close() method to close the file:

            
                              f                .close()            
                          Lawmaking linguistic communication:              CSS              (              css              )                      

To shut the file automatically without calling the close() method, y'all employ the with argument like this:

            
                              with                open(path_to_file)                as                f:     contents = f.readlines()            
                          Lawmaking linguistic communication:              JavaScript              (              javascript              )                      

In practice, you'll use the with statement to close the file automatically.

Reading a text file examples

We'll apply the-zen-of-python.txt file for the demonstration.

The following example illustrates how to use the read() method to read all the contents of the the-zen-of-python.txt file into a cord:

            
                              with                open('the-zen-of-python.txt')                every bit                f:     contents = f.read()     print(contents)            
                          Lawmaking linguistic communication:              JavaScript              (              javascript              )                      

Output:

            
              Cute is improve than ugly. Explicit is better than implicit. Simple is amend than complex. ...                          
          

The following example uses the readlines() method to read the text file and returns the file contents as a listing of strings:

            
              lines = []                with                open up('the-zen-of-python.txt')                as                f:     lines = f.readlines()  count =                0                for                line                in                lines:     count +=                1                print(f'line {count}: {line}')                          
                          Code language:              JavaScript              (              javascript              )                      

Output:

            
              line 1: Beautiful is better than ugly.  line 2: Explicit is meliorate than implicit.  line three: Simple is ameliorate than complex. ...                          
          

The post-obit instance shows how to use the readline() to read the text file line by line:

            
                              with                open('the-zen-of-python.txt')                every bit                f:     line = f.readline()                while                line:         line = f.readline()         print(line)            
                          Code linguistic communication:              JavaScript              (              javascript              )                      

Output:

            
              Explicit is meliorate than implicit.  Uncomplicated is improve than circuitous.  Complex is amend than complicated. ...                          
          

A more concise way to read a text file line past line

The open up() function returns a file object which is an iterable object. Therefore, y'all can utilize a for loop to iterate over the lines of a text file as follows:

            
                              with                open('the-zen-of-python.txt')                as                f:                for                line                in                f:         print(line)            
                          Code linguistic communication:              JavaScript              (              javascript              )                      

This is more than curtailed way to read a text file line by line.

Read UTF-8 text files

The code in the previous examples works fine with ASCII text files. Nevertheless, if you're dealing with other languages such as Japanese, Chinese, and Korean, the text file is not a simple ASCII text file. And it'southward probable a UTF-8 file that uses more than only the standard ASCII text characters.

To open a UTF-viii text file, you need to pass the encoding='utf-eight' to the open() function to instruct it to expect UTF-8 characters from the file.

For the demonstration, you lot'll use the following quotes.txt file that contains some quotes in Japanese.

The post-obit shows how to loop through the quotes.txt file:

            
                              with                open('quotes.txt', encoding='utf8')                every bit                f:                for                line                in                f:         print(line.strip())                          
                          Lawmaking language:              JavaScript              (              javascript              )                      

Output:

Summary

• Use the open() role with the 'r' mode to open a text file for reading.
• Use the read(), readline(), or readlines() method to read a text file.
• Always close a file later completing reading it using the close() method or the with argument.
• Use the encoding='utf-8' to read the UTF-8 text file.

Did you lot observe this tutorial helpful ?

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Source: https://www.pythontutorial.net/python-basics/python-read-text-file/

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