Read all content file python

Python Read Text file

Python provides built-in functions to perform file operations, such as creating, reading, and writing files. There are mainly two types of files that Python can handle, normal text files and binary files. In this tutorial, we will take a look at how to read text files in Python.

Steps to Read Text File in Python

In Python, to read a text file, you need to follow the below steps.

Step 1: The file needs to be opened for reading using the open() method and pass a file path to the function.

Step 2: The next step is to read the file, and this can be achieved using several built-in methods such as read() , readline() , readlines() .

Step 3: Once the read operation is performed, the text file must be closed using the close() function.

Now that we have seen the steps to read the file content let’s understand each of these methods before getting into examples.

Python open() function

The open() function opens the file if possible and returns the corresponding file object.

Syntax – open(file, mode=’r’, buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

The open() function has a lot of parameters. Let’s take a look at the necessary params for reading the text file. It opens the file in a specified mode and returns a file object.

• file – path like object which represents the file path
• mode (Optional) – The mode is an optional parameter. It’s a string that specifies the mode in which you want to open the file.

Methods for Reading file contents

1. read() : The read() function returns the read bytes in the form of string. This method is useful when you have a small file, and you want to read the specified bytes or entire file and store it into a string variable.
2. readline() : The readline() function returns one line from a text file and retuns in the form of string.
3. readlines() : The readlines() function reads all the lines from the text file and returns each line as a string element in a list.

Python close() function

The file will remain open until you close the file using the close() function. It is a must and best practice to perform this operation after reading the data from the file as it frees up the memory space acquired by that file. Otherwise, it may cause an unhandled exception.

Examples for Reading a Text file in Python

Example 1 – Read the entire text file using the read() function

In the below example, we are reading the entire text file using the read() method. The file can be opened in the read mode or in a text mode to read the data, and it can be stored in the string variable.

# Program to read the entire file using read() function file = open("python.txt", "r") content = file.read() print(content) file.close() # Program to read the entire file (absolute path) using read() function file = open("C:/Projects/Tryouts/python.txt", "r") content = file.read() print(content) file.close()

Dear User, Welcome to Python Tutorial Have a great learning . Cheers

Example 2 – Read the specific length of characters in a text file using the read() function

There are times where you need to read the specific bytes in a file. In that case, you can use the read() function by specifying the bytes. The method will output only the specified bytes of characters in a file, as shown below.

# Program to read the specific length # of characters in a file using read() function file = open("python.txt", "r") content = file.read(20) print(content) file.close() 

Example 3 – Read a single line in a file using the readline() function

If you want to read a single line in a file, then you could achieve this using readline() function. You also use this method to retrieve specific bytes of characters in a line, similar to the read() method.

# Program to read single line in a file using readline() function file = open("python.txt", "r") content = file.readline() print(content) file.close()

Example 4- Read text file line by line using the readline() function

If you want to traverse the file line by line and output in any format, then you could use the while loop with the readline() method as shown below. This is the most effective way to read the text file line by line in Python.

# Program to read all the lines in a file using readline() function file = open("python.txt", "r") while True: content=file.readline() if not content: break print(content) file.close() 

Dear User, Welcome to Python Tutorial Have a great learning . Cheers

Example 5 – Read all the lines as a list in a file using the readlines() function

The readlines() method will read all the lines in the file and outputs in a list of strings, as shown below. Later you can use the list to traverse and extract the specified content from the list.

# Program to read all the lines as a list in a file # using readlines() function file = open("python.txt", "r") content=file.readlines() print(content) file.close() 

['Dear User,\n', 'Welcome to Python Tutorial\n', 'Have a great learning . \n', 'Cheers']

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Python Read Text File

Summary: in this tutorial, you learn 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 string:

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

Steps for reading a text file in Python

To read a text file in Python, you follow these steps:

• First, open a text file for reading by using the open() function.
• 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.

1) open() function

The open() function has many parameters but you’ll be focusing on the first two:

open(path_to_file, mode)Code language: Python (python)

The path_to_file parameter specifies the path to the text file.

If the program and file are in the same folder, you need to specify only the filename of the file. Otherwise, you need to include the path to the file as well as the filename.

To specify the path to the file, you use the forward-slash ( ‘/’ ) even if you’re working on Windows.

For example, if the file readme.txt is stored in the sample folder as the program, you need 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 mode in which you want to open the file. The following table shows available modes for opening a text file:

Mode	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 example, to open a file whose name is the-zen-of-python.txt stored in the same folder as the program, you use the following code:

 f = open('the-zen-of-python.txt','r')Code language: Python (python)

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

2) Reading text methods

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

• read(size) – read some contents of a file based on the optional size and return the contents as a string. If you omit the size, the read() method reads from where it left off till the end of the file. If the end of a file has been reached, the read() method returns an empty string.
• readline() – read a single line from a text file and return the line as a string. If the end of a file has been reached, the readline() returns an empty string.
• readlines() – read all the lines of the text file into a list of strings. This method is useful if you have a small file and you want to manipulate the whole text of that file.

3) close() method

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

It’s important to close the file that is no longer in use for the following reasons:

• First, when you open a file in your script, the file system usually locks it down so no other programs or scripts can use it until you close it.
• Second, your file system has a limited number of file descriptors that you can create before it runs out of them. Although this number might be high, it’s possible to open a lot of files and deplete your file system resources.
• Third, leaving many files open may lead to race conditions which occur when multiple processes attempt to modify one file at the same time and can cause all kinds of unexpected behaviors.

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

f.close()Code language: Python (python)

To close the file automatically without calling the close() method, you use the with statement like this:

with open(path_to_file) as f: contents = f.readlines()Code language: Python (python)

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

Reading a text file examples

We’ll use 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 string:

with open('the-zen-of-python.txt') as f: contents = f.read() print(contents)Code language: Python (python)

Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. . Code language: Python (python)

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

with open('the-zen-of-python.txt') as f: [print(line) for line in f.readlines()]Code language: Python (python)

Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. . Code language: Python (python)

The reason you see a blank line after each line from a file is that each line in the text file has a newline character (\n). To remove the blank line, you can use the strip() method. For example:

with open('the-zen-of-python.txt') as f: [print(line.strip()) for line in f.readlines()]Code language: Python (python)

The following example shows how to use the readline() to read the text file line by line:

with open('the-zen-of-python.txt') as f: while True: line = f.readline() if not line: break print(line.strip())Code language: Python (python)

Explicit is better than implicit. Complex is better than complicated. Flat is better than nested. . Code language: Python (python)

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

The open() function returns a file object which is an iterable object. Therefore, you can use 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.strip())Code language: Python (python)

This is a more concise 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. However, 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’s likely a UTF-8 file that uses more than just the standard ASCII text characters.

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

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

The following shows how to loop through the quotes.txt file:

with open('quotes.txt', encoding='utf8') as f: for line in f: print(line.strip())Code language: Python (python)

Summary

• Use the open() function 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 after completing reading it using the close() method or the with statement.
• Use the encoding=’utf-8′ to read the UTF-8 text file.

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