Question

Assume that the file data.txt exists and contains several lines of text. Write a short program using the while loop that displays each line in the file.

Short answer

Question: Write a Python program that reads and displays the contents of a text file called data.txt using a while loop, and explain the steps involved in the process. Answer: To read and display the contents of "data.txt" using a while loop, follow these steps: 1. Open the file using the open() function, with "data.txt" as the file name and "r" as the mode, indicating reading. Store the opened file in a variable, like 'file'. ```python file = open("data.txt", "r") ``` 2. Initialize a loop control variable by reading the first line of the file using the readline() method, and store it in a variable like 'line'. ```python line = file.readline() ``` 3. Create a while loop that continues executing until the end of the file. As long as 'line' is not empty, print its content and read the next line using readline(). ```python while line: print(line.strip()) line = file.readline() ``` 4. After the loop finishes, close the file using the close() method to release system resources. ```python file.close() ``` The complete program reads and displays each line from the data.txt file using a while loop: ```python file = open("data.txt", "r") line = file.readline() while line: print(line.strip()) line = file.readline() file.close() ```

Step-by-step solution

Open the file

To read and process the file, you must first open it using the open() function. The open() function takes two parameters: the name of the file you want to open and the mode you want to open it in. In this case, the filename is "data.txt" and the mode is "r" for reading. Store the opened file in a variable, here we will use the variable 'file'. ```python file = open("data.txt", "r") ```

Initialize loop control variable

Now, you need to initialize a loop control variable to control the while loop. Start by reading the first line of the file using the readline() method. Store the read line in a variable, which we'll call 'line'. ```python line = file.readline() ```

Create the while loop

Next, create a while loop that continues executing until the end of the file is reached. To do this, use a loop that continues to execute as long as the content of the 'line' variable is not empty. Inside the loop, print the content of 'line' and then read the next line of the file by calling readline() and storing the result in the 'line' variable. ```python while line: print(line.strip()) line = file.readline() ```

Close the file

Once the loop is finished and all lines in the file have been printed, close the file using the close() method to release any system resources tied to it. ```python file.close() ```

Full program

Here is the complete program: ```python file = open("data.txt", "r") line = file.readline() while line: print(line.strip()) line = file.readline() file.close() ``` This program will read and display each line from the data.txt file using a while loop.