Python Lists: Transform Values with Explicit Loops

A sensor reports Celsius values that need Fahrenheit equivalents.

What You Need to Understand

Transforming a list means generating one new value for each original value. An explicit loop makes the steps visible before introducing a list comprehension.

When to Use It

A sensor reports Celsius values that need Fahrenheit equivalents.

Step-by-Step Python Example

celsius_values = [0, 20, 30]
fahrenheit_values = []
for celsius in celsius_values:
    fahrenheit_values.append(celsius * 9 / 5 + 32)
print(fahrenheit_values)

How the Example Works

Each input contributes one transformed result; the output list has the same length and order as the input.

Example Output

[32.0, 68.0, 86.0]
[45.0, 90.0]

A Second Example

Compare this smaller variation with the main example, then experiment with your own values.

prices = [50, 100]
print([price * 0.9 for price in prices])

Important Behavior and Edge Cases

If the transformation changes units, name your variables to show which unit each value uses.

Try It Yourself

Convert a list of prices into prices with a 10 percent discount.

Common Beginner Mistakes

If the transformation changes units, name your variables to show which unit each value uses.
Overlooking how an iterable is consumed, how element positions are chosen, or whether a function creates a new list.

Key Takeaways

Transforming a list means generating one new value for each original value.
Each input contributes one transformed result; the output list has the same length and order as the input.
If the transformation changes units, name your variables to show which unit each value uses.