CODEWITHSUNDEEP
python
Mr. Lance E Sloan
Mr. Lance E Sloan

Reputation: 3387

Why are strings favored over defined symbols (constants)?

I notice that Python frequently uses strings where you could use some kind of defined symbol, like a constant. For example, to paraphrase a sample of code from argparse:

import argparse

parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument('--sum', dest='accumulate', action='store_const',
                    const=sum, default=max,
                    help='sum the integers (default: find the max)')

Rather than requiring the use of the string 'store_const', why didn't the developers define a constant-like symbol, e.g. ArgumentParser.STORE_CONST?

I'd prefer the constant because code editors can easily see them in the module and use them as suggestions for code completions. Also, a typo in a string may not cause an error, but a typo in a defined symbol probably would. I've seen several examples in Python of strings used this way, but it's not as common in other languages, like Java or PHP.

Upvotes: 0

Views: 56

Answers (1)

Joran Beasley
Joran Beasley

Reputation: 113930

many libraries do use "constants" ... including argparse

you could just as easily pass in argparse._StoreConstAction

it also provides the following named constants

SUPPRESS = '==SUPPRESS=='

OPTIONAL = '?'
ZERO_OR_MORE = '*'
ONE_OR_MORE = '+'
PARSER = 'A...'
REMAINDER = '...'
_UNRECOGNIZED_ARGS_ATTR = '_unrecognized_args'

another option would be to write your own constants class that encompasses all of the magic numbers and or strings that bother you

Upvotes: 1

Related Questions