File Handling in Python: Create, Open, Append, Read, Write

Introduction

File handling is an integral part of programming. File handling in Python is simplified with built-in methods, which include creating, opening, and closing files.

While files are open, Python additionally allows performing various file operations, such as reading, writing, and appending information.

This article teaches you how to work with files in Python.

Prerequisites

• Python 3 installed and set up.
• An IDE or code editor to write code.
• Access to a terminal to run the code (or run directly in an IDE).
• A text file for the examples.

Opening Files in Python

The open() Python method is the primary file handling function. The basic syntax is:

file_object = open('file_name', 'mode')

The open() function takes two elementary parameters for file handling:

1. The file_name includes the file extension and assumes the file is in the current working directory. If the file location is elsewhere, provide the absolute or relative path.

2. The mode is an optional parameter that defines the file opening method. The table below outlines the different possible options:

The mode must have exactly one create(x)/read(r)/write(w)/append(a) method, at most one +. Omitting the mode defaults to 'rt' for reading text files.

Below is a table describing how each of the modes behave when invoked.

Read Mode

The read mode in Python opens an existing file for reading, positioning the pointer at the file's start.

To read a text file in Python, load the file by using the open() function:

f = open("<file name>")

The mode defaults to read text ('rt'). Therefore, the following method is equivalent to the default:

f = open("<file name>", "rt")

To read files in binary mode, use:

f = open("<file name>", "rb")

Add + to open a file in read and write mode:

f = open("<file name>", "r+")  # Textual read and write

f = open("<file name>", "rt+") # Same as above

f = open("<file name>", "rb+") # Binary read and write

In all cases, the function returns a file object and the characteristics depend on the chosen mode.

Write Mode

Write mode creates a file for writing content and places the pointer at the start. If the file exists, write truncates (clears) any existing information.

To open a file for writing information, use:

f = open("<file name>", "w")

The default mode is text, so the following line is equivalent to the default:

f = open("<file name>", "wt")

To write in binary mode, open the file with:

f = open("<file name>", "wb")

Add + to allow reading the file:

f = open("<file name>", "w+")  # Textual write and read

f = open("<file name>", "wt+") # Same as above

f = open("<file name>", "wb+") # Binary write and read

The open() function returns a file object whose details depend on the chosen modes.

Append Mode

Append mode adds information to an existing file, placing the pointer at the end. If a file does not exist, append mode creates the file.

Use one of the following lines to open a file in append mode:

f = open("<file name>", "a")  # Text append

f = open("<file name>", "at") # Same as above

f = open("<file name>", "ab") # Binary append

Add the + sign to include the read functionality.

Create Mode

Create mode (also known as exclusive create) creates a file only if it doesn't exist, positioning the pointer at the start of the file.

Use one of the following lines to open a file in create mode:

f = open("<file name>", "x")  # Text create

f = open("<file name>", "xt") # Same as above

f = open("<file name>", "xb") # Binary create

Add the + sign to the mode include reading functionality to any of the above lines.

Reading Files in Python

After importing a file into an object, Python offers numerous methods to read the contents.

Use the read() method on the file object and print the result. For example:

f = open("file.txt")
print(f.read(),end="")

The code prints the text file's contents.

Read Parts of the File

Provide a number to the read() function to read only the specified number of characters:

f = open("file.txt")
print(f.read(5))

The output prints the first five characters in the file.

Alternatively, use the readline() method to print only the first line of the file:

f = open("file.txt")
print(f.readline())

Add an integer to the readline() function to print the specified number of characters without exceeding the first line.

Read Lines

To read lines and iterate through a file's contents, use a for loop:

f = open("file.txt")
for line in f:
    print(line, end="")

Alternatively, use the readlines() method on the file object:

f = open("file.txt")
print(f.readlines())

The function returns the list of lines from the file stream.

Add an integer to the readlines() function to control the number of lines. For example:

f = open("file.txt")
print(f.readlines(15))

The integer represents the character number, and the function returns the line where the character ends along with the previous lines.

Close Files

A file remains open until invoking the close() function. It's good practice to close files no longer in use to avoid unpredictable file behavior and corrupted files.

To close a file, run the close() method on the file object:

f.close()

An alternative way to ensure a file closes is to use the with statement. For example:

with open("<file name>"):
    file_contents = f.read()
    # Additional code here

The with statement automatically closes the file.

Deleting Files in Python

Removing files in Python requires establishing communication with the operating system. Import the os library and delete a file with the following:

import os
os.remove("file.txt")

The file is no longer available. If the file does not exist, Python throws an error.

Python File Methods

Python offers various other functions when working with file objects. Below is a table that outlines all available processes and what they do.

Conclusion

You know how to handle files in Python after reading this guide. Try using a Python library such as Pandas to work with other file types.

For more Python tutorials refer to our article and find out how to add items to Python dictionary.