Regular Expression Puzzles and AI Coding Assistants by David Q. Mertz

Author:David Q. Mertz [Mertz, David Q.]
Language: eng
Format: epub, pdf
Publisher: Manning Publications Co.
Published: 0101-01-01T00:00:00+00:00

Author thoughts Functions are a big help in larger programs

The truth is, we do not genuinely need regular expressions for either of these support functions. But we do have the opportunity to use them. First let’s transform any ASCII version of a hand into the Unicode version. Along the way, we make sure the hand consists of five valid ASCII cards:

def prettify(hand): assert re.search(r'^([2-9TJQKA][SHDC] ?){5}$', hand) symbols = {'S': '♠', 'H': '♥', 'D': '♦', 'C': '♣'} for let, suit in symbols.items(): hand = re.sub(let, suit, hand) return hand

Sorting uses mostly plain Python techniques. In particular, we can rely on the fact that Python’s sort is stable. This means the order will not change between equivalent elements. Therefore, sorting first by suit, then by number will be guaranteed to have the right overall effect:

def cardsort(hand): def by_num(card): map = {'T':'A', 'J':'B', 'Q':'C', 'K':'D', 'A':'E'} num = card[0] return num if num not in 'AKQJT' else map[num] def by_suit(card): map = {'♣': 1, '♦': 2, '♥': 3, '♠': 4} return map[card[1]] hand = re.split(' ', hand) hand.sort(key=by_suit, reverse=True) hand.sort(key=by_num, reverse=True) return ' '.join(hand)

Combining these:

>>> cardsort(prettify('8C AS 4H KS 2C')) 'A♠ K♠ 8♣ 4♥ 2♣'

We will need more regular expressions in the next few puzzles which continue this poker theme.

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