Change case of all characters in a .txt file using Python

In this article, we will learn how to change the case of all characters present in a text file using Python. We will use Python methods Python upper() to change all characters to upper case, and Python lower() to change all characters to lower case.

For example, If we have text file data.txt as shown below.

Change all characters to uppercase from the text file

In this method, we will read line by line from the text file and change the case, and write that line to a new text file. We will read each line from this file, change the case and write it into an output.txt file.

Output:

• Open files in read and append mode: The code opens data.txt in read mode and output.txt in append mode. This allows reading data from the source file and adding content to the output file without overwriting it.
• Iterate through each line: For each line in data.txt, the program reads the content and processes it by converting the text to uppercase using the upper() method.
• Write the modified line: After converting the line to uppercase, the modified line is written into output.txt using output_file.write().

Change all characters to lowercase from the text file

In this method, we will read the entire file, convert the case of all characters and write it into the new file. Here also we will take the same txt file data.txt and read the entire file and convert characters to lowercase using the lower() method and write to the output.txt file.

Output:

Explanation:

• Open files in read and append mode: The code opens data.txt in read mode and output.txt in append mode, allowing it to read the content from the source file and append the modified content to the output file without overwriting existing data.
• Read and convert content: The data_file.read() method reads the entire content of data.txt as a single string, and the lower() method converts all the text to lowercase.
• Write modified content: The converted lowercase content is then written to output.txt using output_file.write(), appending the modified content to the file.

Capitalize the first letter of each word from the text file

We will use an inbuilt method to capitalize the first letter of each word in data.txt. By looping through each word, we will modify the case of the first letter and write the changes to an output file.

Output:

• Open files: data.txt is opened for reading and output.txt for appending.
• Process each line: The line is split into words, and each word's first letter is capitalized.
• Write to output: The modified line is joined and written to output.txt