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| def fenPass(fen): | |
| """ | |
| """ | |
| regexMatch=re.match('\s*^(((?:[rnbqkpRNBQKP1-8]+\/){7})[rnbqkpRNBQKP1-8]+)\s([b|w])\s([K|Q|k|q]{1,4})\s(-|[a-h][1-8])\s(\d+\s\d+)$', fen) | |
| if regexMatch: | |
| regexList = regexMatch.groups() | |
| fen = regexList[0].split("/") | |
| if len(fen) != 8: | |
| raise ValueError("expected 8 rows in position part of fen: {0}".format(repr(fen))) | |
| for fenPart in fen: | |
| field_sum = 0 | |
| previous_was_digit, previous_was_piece = False,False | |
| for c in fenPart: | |
| if c in ["1", "2", "3", "4", "5", "6", "7", "8"]: | |
| if previous_was_digit: | |
| raise ValueError("two subsequent digits in position part of fen: {0}".format(repr(fen))) | |
| field_sum += int(c) | |
| previous_was_digit = True | |
| previous_was_piece = False | |
| elif c == "~": | |
| if not previous_was_piece: | |
| raise ValueError("~ not after piece in position part of fen: {0}".format(repr(fen))) | |
| previous_was_digit, previous_was_piece = False,False | |
| elif c.lower() in ["p", "n", "b", "r", "q", "k"]: | |
| field_sum += 1 | |
| previous_was_digit = False | |
| previous_was_piece = True | |
| else: | |
| raise ValueError("invalid character in position part of fen: {0}".format(repr(fen))) | |
| if field_sum != 8: | |
| raise ValueError("expected 8 columns per row in position part of fen: {0}".format(repr(fen))) | |
| else: raise ValueError("fen doesn`t match follow this example: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 ") | |
| def main(): | |
| try: | |
| fenPass('rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1') | |
| except ValueError as e: | |
| print e.message | |
| if __name__ == '__main__': | |
| main() |
Great work! Thanks for sharing!
One missing piece that I noticed, is that on the Castle portion of the FEN regex, there's also the option of no Castle at all, which would be '-'.
To fix that, just add the -| like in the following two portions. Here is the fixed regex:
\s*^(((?:[rnbqkpRNBQKP1-8]+\/){7})[rnbqkpRNBQKP1-8]+)\s([b|w])\s(-|[K|Q|k|q]{1,4})\s(-|[a-h][1-8])\s(\d+\s\d+)$
Here is a FEN that can be used to test that:
r4rk1/pbqn1pp1/1pn1p2p/2ppP2Q/3P4/2PBP1B1/PP1N2PP/R4RK1 w - - 0 14
I'm really confused by the lines 22-25.
In no documentation I can find something about a valid character "~".
Can you explain, whats it meaning is?
@PanCave You can remove the condition since it is redundant. The regex expression matching will never allow ~ in the FEN notation
For regexList = regexMatch.groups(), it may be better to replace this with regexList = fen.split().
For this FEN: "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1", regexMatch.groups() sets regexList equal to:
["rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR", "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/", "w", "KQkq", "-", "0 1"]
In the gist provided this doesn't make any difference, but if someone wanted to test more than the first portion of their FEN, the subsequent elements might not be what they expect. In terms of FEN notation, the second element shouldn't exist, and the "0 1" should be two different elements.
This is really helpful. Thanks!