40 lines
2.1 KiB
Python
40 lines
2.1 KiB
Python
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from functools import reduce
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cons = lambda h, t: [h, *t]
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postpend = lambda l, e: [*l, e]
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parse_tok = lambda t: lambda s: [(t, s[len(t):])] if s.startswith(t) else []
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parse_except = lambda e: lambda s: [(s[0], s[1:])] if len(s) > 0 and s[0] not in e else []
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parse_eof = lambda s: [('<EOF>', "")]if len(s) == 0 else []
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parse_altl = lambda a, b: lambda s: (lambda ra: ra if len(ra) > 0 else b(s))(a(s))
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parse_seq = lambda f: lambda a, b: lambda s: [(f(v1, v2), r2) for (v1, r1) in a(s) for (v2, r2) in b(r1)]
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parse_seql = parse_seq(lambda l, r: l)
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parse_seqr = parse_seq(lambda l, r: r)
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parse_pure = lambda v: lambda s: [(v, s)]
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parse_map = lambda f, a: lambda s: [(f(v), r) for (v, r) in a(s)]
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parse_many = lambda a: parse_altl(parse_seq(cons)(a, lambda s: parse_many(a)(s)), parse_pure([]))
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parse_many_sep = lambda sep: lambda a: parse_altl(parse_seq(postpend)(parse_many(parse_seql(a, sep)), a), parse_pure([]))
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parse_any_tok = lambda *ts: reduce(parse_altl, [parse_tok(t) for t in ts], lambda s: [])
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parse_whitespace = parse_many(parse_tok(' '))
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parse_dbqt = parse_tok('"')
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parse_str_char = parse_except('"')
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parse_newline = parse_any_tok('\r\n', '\n', '\r')
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parse_escaped_quote = parse_map(lambda _: '"', parse_tok('""'))
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parse_quoted = parse_seql(parse_seqr(parse_seqr(parse_whitespace, parse_dbqt), parse_many(parse_altl(parse_str_char, parse_escaped_quote))), parse_seql(parse_dbqt, parse_whitespace))
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parse_unquoted = parse_many(parse_except('"\r\n,'))
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parse_field = parse_map(lambda chars: ''.join(chars), parse_altl(parse_quoted, parse_unquoted))
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parse_line = parse_many_sep(parse_tok(','))(parse_field)
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parse_lines = parse_many_sep(parse_newline)(parse_line)
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trim_final_empty_line = lambda lines: lines[:-1] if len(lines)>0 and lines[-1] in [[""],[]] else lines
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parse_csv = parse_seql(parse_map(trim_final_empty_line, parse_lines), parse_eof)
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def read_csv_file(file_path):
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with open(file_path, 'r') as file:
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parse_results = parse_csv(file.read())
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return parse_results[0][0] if len(parse_results) else None
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parsed_table = read_csv_file("./my_data.csv")
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print(f'Row 3, Column D reads: {parsed_table[2][3]}')
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