String Methods and Formatting

Unit ID: M02-U05 Estimated active time: 22-30 minutes

Clean text in visible steps

Real text often contains inconsistent spaces or letter case.

raw_status = "  PLANNED  "
clean_status = raw_status.strip().lower()
print(clean_status)

Output:

planned

strip() removes whitespace at the beginning and end. lower() creates a lowercase version. The original string remains unchanged.

Other useful methods include:

text = "python foundations"
print(text.upper())
print(text.title())
print(text.replace("foundations", "practice"))
print(text.startswith("python"))
print(text.endswith("practice"))

Methods are called with dot notation: the object, a dot, and the method name.

Chaining methods

This code applies two operations in sequence:

clean_name = "  python foundations  ".strip().title()
print(clean_name)

Output:

Python Foundations

Use short chains when each step remains clear. For a complex cleaning rule, use separate named steps so you can inspect the intermediate values.

Format output with f-strings

An f-string places values inside readable text:

course_name = "Python Foundations for AI"
course_hours = 32
print(f"{course_name} has {course_hours} course hours.")

Output:

Python Foundations for AI has 32 course hours.

The leading f tells Python to evaluate expressions inside braces.

Format numbers for display

average_hours = 32 / 9
print(f"Average hours per module: {average_hours:.2f}")

The display shows two digits after the decimal point. The underlying value in average_hours has not been changed.

Display formatting and calculation rules are different. Do not use formatted text as though it were still a number.

Quotes inside strings

Use one quotation style around text containing the other:

message = "Python's rules are learnable."
quote = 'The learner said, "I can trace this."'

You can also escape a matching quote with a backslash, but choose the clearest readable form.

Practice

Start with:

raw_course = "  PYTHON foundations FOR ai  "
course_hours = 32

Create a cleaned lowercase version, then create a display version using .title(). Notice that .title() produces Ai, not the abbreviation AI. Correct the display value with .replace("Ai", "AI").

Print:

Course: Python Foundations For AI | Course hours: 32

Then explain why the cleaning value and display value may be kept separately.

Takeaway

String methods create cleaned or transformed text. F-strings combine values into readable output without unsafe text-number concatenation. Inspect intermediate values when a cleaning rule has several steps. Next, we will distinguish missing information from zero and empty text.