Python File Operations - Read and Write to files with Python

In this tutorial, we’ll work on the different file operations in Python. We’ll go over how to use Python to read a file, write to a file, delete files, and much more. So without any delay, let’s get started.

Working with Files in Python

In the previous tutorial, we used console to take input. Now, we will be taking input using a file. That means, we will read from and write into files. To do so, we need to maintain some steps. Those are

1. Open a file
2. Take input from that file / Write output to that file
3. Close the file

We will also learn some useful operations such as copy file and delete file.

Why are file operations in Python needed?

When working with large datasets in machine learning problems, working with files is a basic necessity. Since Python is a majorly used language for data science, you need to be proficient with the different file operations that Python offers.

So, let’s explore some of the Python file operations here.

1. Open a file in Python with the open() function

The first step to working with files in Python is to learn how to open a file. You can open files using the open() method.

The open() function in Python accepts two arguments. The first one is the file name along with the complete path and the second one is the file open mode.

Below, I’ve listed some of the common reading modes for files:

• ‘r’ : This mode indicate that file will be open for reading only
• ‘w’ : This mode indicate that file will be open for writing only. If file containing containing that name does not exists, it will create a new one
• ‘a’ : This mode indicate that the output of that program will be append to the previous output of that file
• ‘r+’ : This mode indicate that file will be open for both reading and writing

Additionally, for the Windows operating system, you can append ‘b’ for accessing the file in binary. This is is because Windows differentiates between a binary text file and a regular text file.

Suppose, we place a text file name ‘file.txt’ in the same directory where our code is placed. Now we want to open that file.

However, the open(filename, mode) function returns a file object. With that file object you can proceed your further operation.

#directory:   /home/imtiaz/code.py
text_file = open('file.txt','r')

#Another method using full location
text_file2 = open('/home/imtiaz/file.txt','r')
print('First Method')
print(text_file)

print('Second Method')
print(text_file2)

The output of the following code will be

================== RESTART: /home/imtiaz/code.py ==================
First Method

Second Method

>>>

2. Read and write to files in Python

Python offers various methods to read and write to files where each functions behaves differently. One important thing to note is the file operations mode. To read a file, you need to open the file in the read or write mode. While to write to a file in Python, you need the file to be open in write mode.

Here are some of the functions in Python that allow you to read and write to files:

• read() : This function reads the entire file and returns a string
• readline() : This function reads lines from that file and returns as a string. It fetch the line n, if it is been called nth time.
• readlines() : This function returns a list where each element is single line of that file.
• readlines() : This function returns a list where each element is single line of that file.
• write() : This function writes a fixed sequence of characters to a file.
• writelines() : This function writes a list of string.
• append() : This function append string to the file instead of overwriting the file.

Let’s take an example file “abc.txt”, and read individual lines from the file with a for loop:

#open the file
text_file = open('/Users/pankaj/abc.txt','r')

#get the list of line
line_list = text_file.readlines();

#for each line from the list, print the line
for line in line_list:
    print(line)

text_file.close() #don't forget to close the file

Output:

Now, that we know how to read a file in Python, let’s move ahead and perform a write operation here with the writelines() function.

#open the file
text_file = open('/Users/pankaj/file.txt','w')

#initialize an empty list
word_list= []

#iterate 4 times
for i in range (1, 5):
    print("Please enter data: ")
    line = input() #take input
    word_list.append(line) #append to the list


text_file.writelines(word_list) #write 4 words to the file

text_file.close() #don’t forget to close the file

Output

3. Copy files in Python using the shutil() method

We can use the shutil module to copy files in Python. This utility allows us to perform copy and move operations in Python on different files. Let’s work on this with an example:

import shutil

shutil.copy2('/Users/pankaj/abc.txt', '/Users/pankaj/abc_copy2.txt')

#another way to copy file

shutil.copyfile('/Users/pankaj/abc.txt', '/Users/pankaj/abc_copyfile.txt')

print("File Copy Done")

4. Delete files in Python with the shutil.os.remove() method

Python’s shutil module offers the remove() method to delete files from the file system. Let’s take a look at how we can perform a delete operation in Python.

import shutil
import os

#two ways to delete file
shutil.os.remove('/Users/pankaj/abc_copy2.txt')

os.remove('/Users/pankaj/abc_copy2.txt')

5. Close an open file in Python with the close() method

When you open a file in Python, it’s extremely important to close the file after you make the changes. This saves any changes that you’ve previously made, removes the file from the memory, and prevents any further reads or writes within the program.

Syntax to close an open file in Python:

fileobject.close()

If we continue on from our previous examples where we read files, here’s how you’d close the file:

text_file = open('/Users/pankaj/abc.txt','r')
# some file operations here

text_file.close()

Additionally, you can avoid closing files manually if you use the with block. As soon as the with block is executed, the files are closed and are no longer available for reading and writing.

6. Python FileNotFoundError

It’s common to receive the FileNotFoundError when working with files in Python. It can be easily avoided by providing complete file paths when creating the file object.

  File "/Users/pankaj/Desktop/string1.py", line 2, in <module>
    text_file = open('/Users/pankaj/Desktop/abc.txt','r')
FileNotFoundError: [Errno 2] No such file or directory: '/Users/pankaj/Desktop/abc.txt'

To fix the FileNotFoundError, you simply need to verify that the path you’ve mentioned for the file open method is correct.

Conclusion

These are the file operations on Python. There are many more ways you can use files within Python which includes reading CSV data and more. Here’s an article on how you can use the Pandas module to read CSV datasets in Python.

I hope you enjoyed reading the article! Happy learning :)

**References:
**https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files