Python: Validate String: Lowercase, Digit, Underscore: re.match, bool()

Using re.match to Validate a String

from re import match as m

• import the match() method of the re module (regular expressions)

def validate_str(s):

• defines function named validate_str with the formal parameter named s which becomes a placeholder for the string being validated

return bool(m("[0–9a-z_]{4,16}$", s))

• [0–9a-z_]{4,16}$ is the regex pattern (regular expression) used to match specific string characteristics
• m() is the match method
• bool() returns the Boolean constant True or False. True, if the entire string matches the regex pattern.

Regex Pattern

• [0–9] matches digits
• [a-z] matches lowercase letters
• _ matches underscores
• {4,16} limits string length match from ≥ 4 to ≤ 16
• $ operator indicates the end of the string
• s is placeholder for the string being matched