How do we assign values to variables in a list using a loop in Python?

In Python, lists are a useful way to store multiple elements in a single variable. To assign values to each entry in a list, loops are often needed. This strategy simplifies the process and improves the clarity of your code. This chapter will look at how to assign values to variables in a list using different loop types, using basic examples.

Using Simple Loop Iterations

In this method, we use the while loop to continuously prompt the user for input and append elements to the list. When we do not enter any element into the list and just press the Enter key, the loop breaks. To append the elements to the list, we use the append() method.

Example

The following is an example to assign values to variables in a list using a loop in Python using the append() method −

items_list = []
while True:
    item = input("Enter new item or press enter if you want to exit: ")
    if item == '':
        break
    items_list.append(item)
print("List:", items_list)

When you run the program, it will show this output −

Enter new item or press enter if you want to exit: 5
Enter new item or press enter if you want to exit: 9
Enter new item or press enter if you want to exit: 6
Enter new item or press enter if you want to exit: 
List: ['5', '9', '6']

Using the globals() Method

The globals() method retrieves the current global symbol table's dictionary. A symbol table is a data structure that a compiler maintains, which contains all of the program's necessary information. This method allows you to dynamically create variables from a list of names.

Example

The following is an example to assign values to variables in a list using a loop in Python using the globals() method −

var_names = ["one", "two", "three"]
count = 1
for name in var_names:
    globals()[name] = count
    count += 1
print(one)
print(two)
print(three)

After running the program, you will get this result −

1
2
3

Using List Comprehension

List comprehension provides a concise way to create lists. In this program, we will use list comprehension to create a list of even numbers by iterating through a range and applying a condition.

# Using list comprehension to generate even numbers from 0 to 10
# includes i if it is even
even_numbers = [i for i in range(11) if i % 2 == 0]
print(even_numbers)

This output will be displayed when the program runs −

[0, 2, 4, 6, 8, 10]

Using Nested Loops to Create a Multiplication Table

In this example, we will use nested loops to create a multiplication table. The outer loop iterates through the numbers 1 to 5, and the inner loop multiplies each number by the current number of the outer loop to create rows and columns.

# Creating an empty list for the multiplication table
multiplication_table = []

# Using nested loops to generate the table
for i in range(1, 6):  # Iterate through rows
    row = []  # Create an empty row
    # Iterate over columns
    for j in range(1, 6):  
        # Multiply and add to the current row  
        row.append(i * j)  
    # Append the created row to the table
    multiplication_table.append(row)  

print(multiplication_table)  

You will see this result after executing the program −

[[1, 2, 3, 4, 5], [2, 4, 6, 8, 10], [3, 6, 9, 12, 15], [4, 8, 12, 16, 20], [5, 10, 15, 20, 25]]

Using For Loop with Range

You can also use a for loop with range() to assign values directly to list indices. This approach is useful when you know the size of the list in advance.

# Create a list with 5 empty elements
numbers = [0] * 5

# Assign values using a for loop
for i in range(len(numbers)):
    numbers[i] = i * 2

print(numbers)

The output will be −

[0, 2, 4, 6, 8]

Conclusion

Python provides multiple ways to assign values to variables in a list using loops. Use simple loops for user input, list comprehension for concise creation, and nested loops for complex data structures like tables.