Question

Assume 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

Answer: To read and display each line from the file "data.txt," follow the steps below: 1. Open the file using the open() function in read mode: ```python file = open('data.txt', 'r') ``` 2. Initialize a variable 'line' to None, and set up a while loop that reads each line and prints it until the readline() method returns an empty string: ```python line = None while line != '': line = file.readline() print(line) ``` 3. Close the file to free up any associated resources using the close() method: ```python file.close() ``` Combining these steps, the full program would look like this: ```python file = open('data.txt', 'r') line = None while line != '': line = file.readline() print(line) file.close() ```

Step-by-step solution

Open the file data.txt

To read the content of the file, we first have to open it using the open() function in read mode (indicated by 'r') like this: ```python file = open('data.txt', 'r') ```

Set up the while loop

We'll now set up a while loop that reads each line and, for the time being, just prints it. We will start by initializing a variable 'line' to None, so our loop will continue until the readline() method returns an empty string (indicating the end of the file): ```python line = None while line != '': line = file.readline() print(line) ```

Close the file

After the while loop is finished, we need to close the file to free up any associated resources. We can do this using the close() method on our file object: ```python file.close() ```

Full program

Combining the three previous steps, the full program to display each line in 'data.txt' using a while loop would look like this: ```python file = open('data.txt', 'r') line = None while line != '': line = file.readline() print(line) file.close() ```