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Challenge 166: Hex Validator

curriculum/challenges/english/blocks/daily-coding-challenges-python/696655d24b614176d4c9b789.md

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--description--

Given a string, determine whether it is a valid CSS hex color. A valid CSS hex color must:

  • Start with a #, and
  • be followed by either 3 or 6 hexadecimal characters.

Hexadecimal characters are numbers 0 through 9 and letters a through f (case-insensitive).

--hints--

is_valid_hex("#123") should return True.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(is_valid_hex("#123"), True)`)
}})

is_valid_hex("#123abc") should return True.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(is_valid_hex("#123abc"), True)`)
}})

is_valid_hex("#ABCDEF") should return True.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(is_valid_hex("#ABCDEF"), True)`)
}})

is_valid_hex("#0a1B2c") should return True.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(is_valid_hex("#0a1B2c"), True)`)
}})

is_valid_hex("#12G") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(is_valid_hex("#12G"), False)`)
}})

is_valid_hex("#1234567") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(is_valid_hex("#1234567"), False)`)
}})

is_valid_hex("#12 3") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(is_valid_hex("#12 3"), False)`)
}})

is_valid_hex("fff") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(is_valid_hex("fff"), False)`)
}})

--seed--

--seed-contents--

py
def is_valid_hex(s):

    return s

--solutions--

py
def is_valid_hex(s):
    if not s.startswith("#"):
        return False

    hex_part = s[1:]
    if len(hex_part) not in (3, 6):
        return False

    for char in hex_part:
        if not char.lower() in "0123456789abcdef":
            return False

    return True