Date helpers

Add datetime processing methods.

The format_date method

We'll write a format_date method to show dates in one form. format_date(year, month, day) returns a string in YYYY-MM-DD form; single digit months and days are zero padded.

Example: format_date(2024, 5, 1) → "2024-05-01". We use an f-string with the :02d format: f"{year:04d}-{month:02d}-{day:02d}". :04d pads the year to four digits, :02d pads month/day to two.

f-string formatting

Inside an f-string, {value:format} turns the value into the given format. :02d writes an integer with at least two digits, padded with zeros; :04d pads to four digits.

Example: f"{5:02d}" → "05", f"{2024:04d}" → "2024". Literal characters like - are written as is. This lets us format dates in one line.

Exercise Add format_date to Utility

Add a def format_date(self, year, month, day): method to the Utility class. In the body write return f"{year:04d}-{month:02d}-{day:02d}". Then create an instance with u = Utility() and call print(u.format_date(2024, 5, 1)).

Show example solution

class Utility:
    version = "1.0"
    def slugify(self, text):
        return text.lower().replace(" ", "-")
    def clamp(self, n, lo, hi):
        return max(lo, min(hi, n))
    def format_date(self, year, month, day):
        return f"{year:04d}-{month:02d}-{day:02d}"

u = Utility()
print(u.format_date(2024, 5, 1))

Test yourself

Complete the format_date signature

class Utility:
    def format_date(self, year, month, ____):
        return f"{year:04d}-{month:02d}-{day:02d}"

Show answer

class Utility:
    def format_date(self, year, month, day):
        return f"{year:04d}-{month:02d}-{day:02d}"

Match the format_date parts

format_date

Method name
:02d

Zero padding
2024-05-01

Output
What does format_date(2024, 5, 1) return?
- 2024-5-1
- 2024/05/01
- 05-01-2024
- 2024-05-01
Show answer

2024-05-01 — :02d pads month and day with zeros; the separator is a hyphen.

Next lesson: Putting it together

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