Open a File in Python

In this tutorial, you’ll learn how to open a file in Python.

The data can be in the form of files such as text, csv, and binary files. To extract data from these files, Python comes with built-in functions to open a file and then read and write the file’s contents.

After reading this tutorial, you can learn: –

• How to open a file in Python using both relative and absolute path
• Different file access modes for opening a file
• How to open a file for reading, writing, and appending.
• How to open a file using the with statement
• Importance of closing a file

Access Modes for Opening a file

The access mode parameter in the open() function primarily mentions the purpose of opening the file or the type of operation we are planning to do with the file after opening. in Python, the following are the different characters that we use for mentioning the file opening modes.

File Mode	Meaning
r	Opens a file for reading (default)
w	Open a file for writing. If a file already exists, it deletes all the existing contents and adds new content from the start of the file.
x	Open a file for exclusive creation. If the file already exists, this operation fails.
a	Open a file in the append mode and add new content at the end of the file.
b	Open the file in binary mode.
t	Opens a file in a text mode (default).
+	Open a file for updating (reading and writing).

Steps For Opening File in Python

Example: Opening a File in read mode

The following code shows how to open a text file for reading in Python. In this example, we are opening a file using the absolute Path.

An absolute path contains the entire path to the file or directory that we need to access. It includes the complete directory list required to locate the file.

# Opening the file with absolute path
fp = open(r'E:\demos\files\sample.txt', 'r')
# read file
print(fp.read())
# Closing the file after reading
fp.close()

# path if you using MacOs
# fp = open(r"/Users/myfiles/sample.txt", "r")

Output

Welcome to PYnative.com
This is a sample.txt

Opening a File with Relative Path

A relative path is a path that starts with the working directory or the current directory and then will start looking for the file from that directory to the file name.

For example, reports/sample.txt is a relative path. In the relative path, it will look for a file into the directory where this script is running.

# Opening the file with relative path
try:
    fp = open("sample.txt", "r")
    print(fp.read())
    fp.close()
except FileNotFoundError:
    print("Please check the path.")

Handling the FileNotFoundError

In case we are trying to open a file that is not present in the mentioned path then we will get a FileNotFoundError.

fp = open(r'E:\demos\files\reports.txt', 'r')
print(f.read())

Output

FileNotFoundError: [Errno 2] No such file or directory: 'E:\demos\files\reports.txt'

We can handle the file not found error inside the try-except block. Let us see an example for the same. Use except block to specify the action to be taken when the specified file is not present.

try:
    fp = open(r'E:\PYnative\reports\samples.txt', 'r')
    print(fp.read())
    fp.close()
except IOError:
    print("File not found. Please check the path.")
finally:
    print("Exit")

Output

File not found. Please check the path.
Exit

File open() function

Python provides a set of inbuilt functions available in the interpreter, and it is always available. We don’t have to import any module for that. We can open a file using the built-in function open().

Syntax of the file open() function

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

It return the file object which we can sue to read or write to a file.

Parameters:

Let us see the parameters we can pass to the open() function to enhance the file operation.

Parameter	Description
file	This parameter value gives the pathname (absolute or relative to the current working directory) of the file to be opened.
mode	This is the optional string that specifies the mode in which a file will be opened. The default value is 'r' for reading a text file. We can discuss the other modes in the later section.
buffering	This is an optional integer used to set the buffering policy. Pass 0 to switch buffering off (only allowed in binary mode), 1 to select line buffering (only usable in text mode), and an integer > 1 to indicate the size in bytes of a fixed-size chunk buffer.
encoding	This is the name of the encoding used to decode or encode the file. The default one is platform dependant.
errors	These are optional string denotes how the standard encoding and decoding errors have to be handled.
newline	This is the parameter that indicates how the newline mode works (it only applies to text mode). It can be None, '', '\n', '\r', and '\r\n'.
closefd	This parameter indicates whether to close a file descriptor or not. The default value is True. If closefd is False and a file descriptor rather than a filename was given, the underlying file descriptor will be kept open when the file is closed.

Opening a File in Read mode

We can open a file for reading the contents of a file using the open() function and passing the r mode. This will open the file only for reading the contents, and we can’t use it for anything else like writing new content.

The file can basically in two categories namely flat files and non flat files.

• Flat files are the ones that are not properly indexed, like .csv (comma separated values), where each record has different comma-separated values. But they are not ordered with an index. They generally have one record per line and in general, have a fixed set of values in each record.
• Nonflat files are the ones with proper index values. Each record will have one index value, and we can easily find one using the index value.

Consider that we are having a file called ‘sample.txt’ and we are opening the file for reading its contents.

try:
    fp = open("sample.txt", "r")
    # Reading the contents of the file and closing
    print(fp.read())
    fp.close()
except IOError:
    print("Please check the path.")

Output

Welcome to PYnative.com
This is a sample.txt

Read More: Complete Guide on Reading Files in Python

Opening a File in Write Mode

We can open a file for writing new contents into a file using the open() function with w as the access mode. The cursor or the file pointer will be placed at the beginning of the file.

Note: If the file is already present it will truncate the file, which means all the content previously in the file will be deleted, and the new content will be added to the file.

fp = open("sample2.txt", "w")
# Writing content
fp.write("New line")

# Opening the file again for reading the content
fp = open("sample2.txt", "r")

# Reading the contents of the file and closing
print(fp.read())
fp.close()

Output

New line

Read More: Complete Guide on Write to File in Python

Opening a File in Append Mode

We can append some content at the end of the file using the open() function by passing the character a as the access mode. The cursor will be placed at the end of the file, and the new content will get added at the end.

The difference between this and the write mode is that the file’s content will not be truncated or deleted in this mode.

Consider that the file “sample2.txt” is already created and there is some content in the file. Now we are opening the file in the append mode and trying to add some content at the end of the file.

# Open and Append at last
fp = open("sample2.txt", "a")
fp.write(" Added this line by opening the file in append mode ")

# Opening the file again to read
fp = open("sample2.txt", "r")
print(fp.read())
fp.close()

Closing a File

We need to make sure that the file will be closed properly after completing the file operation. It is a bad practice to leave your files open.

In Python, It is very important to close a file once the job is done mainly for the following reasons: –

• It releases the resources that have been tied up with the file. By this space in the RAM can be better utilized and ensures a better performance.
• It ensures better garbage collection.
• There is a limit to the number of open files in an application. It is always better to close the file to ensure that the limit is not crossed.
• If you open the file in write or read-write mode, you don’t know when data is flushed.

A file can be closed just by calling the close() function as follows.

# Opening the file to read the contents
f = open("sample2.txt", "r")
print(f.read())

# Closing the file once our job is done
f.close()

Opening file using with statement

We can open a file using the with statement along with the open function. The general syntax is as follows.

with open(__file__, accessmode) as f:

The following are the main advantages of opening a file using the with statement

• The with statement simplifies exception handling by encapsulating common preparation and cleanup tasks.
• This also ensures that a file is automatically closed after leaving the block.
• As the file is closed automatically it ensures that all the resources that are tied up with the file are released.

Let us see how we can the with statement for opening a file with an example. Consider there are two files ‘sample.txt’ and ‘sample2.txt’ and we want to copy the contents of the first file to the second.

# Opening file
with open('sample.txt', 'r', encoding='utf-8') as infile, open('sample2.txt', 'w') as outfile:
    # read sample.txt an and write its content into sample2.txt
    for line in infile:
        outfile.write(line)

# Opening the file to read the contents
f = open("Sample2.txt", "r")
print(f.read())
f.close()

Output

Welcome to PYnative.com
File created to demonstrate file handling in Python

Here we can see that the contents of the sample2.txt has been replaced by the contents of sample.txt.

Creating a new file

We can create a new file using the open() function by setting the x mode. This method will ensure that the file doesn’t already exist and then create a new file. It will raise the FileExistsError if the file already exists.

Example: Creating a new file.

try:
    # Creating a new file
    with open("sample3.txt", "x") as fp:
        fp.write("Hello World! I am a new file")

    # reading the contents of the new file
    fp = open("sample3.txt", "r")
    print(fp.read())
except FileExistsError:
    print("The file already exists")

Output

Hello World! I am a new file

Opening a File for multiple operations

In Python, we can open a file for performing multiple operations simultaneously by using the '+' operator. When we pass r+ mode then it will enable both reading and writing options in the file. Let us see this with an example.

with open("Sample3.txt", "r+") as fp:
    # reading the contents before writing
    print(fp.read())

    # Writing new content to this file
    fp.write("\nAdding this new content")

Opening a Binary file

Binary files are basically the ones with data in the Byte format (0’s and 1’s). This generally doesn’t contain the EOL(End of Line) so it is important to check that condition before reading the contents of the file.

We can open and read the contents of the binary file as below.

with open("sample.bin", "rb") as f:
    byte_content = f.read(1)
    while byte_content:
        # Printing the contents of the file
        print(byte_content)

Summary

In this tutorial, we have covered how to open a file using the different access modes. Also, we learned the importance of opening a file using the ‘with’ statement.