what does % stand for in an expression ?

[arbiel]

Hi
I found the following example in the python doc :

from typing import NamedTuple import re class Token(NamedTuple): type: str value: str line: int column: int def tokenize(code): keywords = {'IF', 'THEN', 'ENDIF', 'FOR', 'NEXT', 'GOSUB', 'RETURN'} token_specification = [ ('NUMBER', r'\d+(\.\d*)?'), # Integer or decimal number ('ASSIGN', r':='), # Assignment operator ('END', r';'), # Statement terminator ('ID', r'[A-Za-z]+'), # Identifiers ('OP', r'[+\-*/]'), # Arithmetic operators ('NEWLINE', r'\n'), # Line endings ('SKIP', r'[ \t]+'), # Skip over spaces and tabs ('MISMATCH', r'.'), # Any other character ] tok_regex = '|'.join('(?P<%s>%s)' % pair for pair in token_specification) line_num = 1 line_start = 0 for mo in re.finditer(tok_regex, code): kind = mo.lastgroup value = mo.group() column = mo.start() - line_start if kind == 'NUMBER': value = float(value) if '.' in value else int(value) elif kind == 'ID' and value in keywords: kind = value elif kind == 'NEWLINE': line_start = mo.end() line_num += 1 continue elif kind == 'SKIP': continue elif kind == 'MISMATCH': raise RuntimeError(f'{value!r} unexpected on line {line_num}') yield Token(kind, value, line_num, column) statements = ''' IF quantity THEN total := total + price * quantity; tax := price * 0.05; ENDIF; ''' for token in tokenize(statements): print(token)

Line 22 reads

 tok_regex = '|'.join('(?P<%s>%s)' % pair for pair in token_specification)

I suppose that each %s stands for the corresponding element of pair and that % stands for the tuple itself.

Where can I find any explanation of this coding ?

Thank you for having read my post.

Arbiel

[buran]

Check the docs: Old-style string formatting

Also https://docs.python.org/3/library/stdtyp...formatting

Note, there are newer/better/powerful string formatting methods

[arbiel]

Check the docs: Old-style string formatting

Also https://docs.python.org/3/library/stdtyp...formatting

Note, there are newer/better/powerful string formatting methods

OK

Understood.

Thanks

Arbiel

[carlbidwell]

In Python, the % operator is the modulo operator, it returns the remainder when the left operand is divided by the right operand. For more: Python Forum

[Gribouillis]

Generally speaking

x % y

is equivalent to

x.__mod__(y)

if the type of x implements a __mod__() method. Otherwise it is equivalent to

y.__rmod__(x)

if the type of y implements a __rmod__() method. Otherwise it raises a TypeError.

The effect and result depends on what these methods do, which can be arbitrary.