4 ms·

I just wish python would switch float and Decimal. Most of the time float is just an implementation detail when you really want a decimal. I think the literals

I just wish python would switch float and Decimal. Most of the time float is just an implementation detail when you really want a decimal. I think the literals should be a decimal, and you could explicitly cast float when you actually need to do floating point math, or as an optimization. But I know it's too late for that.

Spivak 5y ago
I mean they switched from strings being bytes of UTF-8 to unicode, never say never for Python 4! It would be a downright Pythonic move.
- tzot 5y ago
  In CPython 2, a `str` was bytes period; no encoding was enforced, these bytes were not necessarily valid UTF-8, and a `unicode` had either UTF-16 or UTF-32 in-memory representation (decided at compilation time). In CPython 3, a `bytes` is bytes and a `str` has ASCII/UTF-16/UTF-32 in-memory representation (decided at runtime). So CPython 2 strings were not “bytes of UTF-8”, and that is why strings `'\xfc\xf7\xe9'` worked fine, they even printed fine in the proper environments.
  - mistrial9 5y ago
    > In CPython 2, a `str` was bytes -- like old C language, a str is really bytes, no encoding is enforced.
amanzi 5y ago
That would suit me too, but not sure of the wider implications.
creata 5y ago
Why do you say that "most of the time... you really want a decimal"? I can't think of any situation where I'd prefer a decimal.Decimal over an ordinary float, except for the textbook example of dollars and cents. In most situations, I'm pretty sure decimal.Decimals would be unacceptably slower.
- tomrod 5y ago
  In data science, this can be an issue.
- samwillis 5y ago
  Even with currency now it seems more common to just use ints of the currency’s lowest denomination/subunit (cents, pence etc)
  - tadfisher 5y ago
    You might as well use a Decimal at that point, which usually combines an integer mantissa with some inverse exponent of 10. Otherwise you're applying that exponent everywhere you use the value, whether you display it or use it in a mathematical expression.
    - samwillis 5y ago
      I think the advantage of ints over Decimal is interoperability of systems. Anything with a REST api or JSON doesn’t have native support for Decimals, so to use them you have to represent them in component form as an object or as a string. Ints just make that easer at the slight cost at display time. Stripe is a good example of this. > Otherwise you're applying that exponent everywhere you use the value, whether you display it or use it in a mathematical expression. Slightly disagree, I think it’s only when displaying you have to convert to a “human readable” decimal form. They don’t need converting to Decimal for processing. It’s also worth noting there are actually two none decimal currency’s still in use: “Today, only two countries have non-decimal currencies: Mauritania, where 1 ouguiya = 5 khoums, and Madagascar, where 1 ariary = 5 iraimbilanja.” https://en.m.wikipedia.org/wiki/Non-decimal_currency https://en.m.wikipedia.org/wiki/Non-decimal_currency
      - creata 5y ago
        > Anything with a REST api or JSON doesn’t have native support for Decimals This is a very slight nitpick (that might be wrong) but I think it's perfectly in line with the JSON specification to interpret JSON numbers as decimals.
munificent 5y ago
My understanding is that even decimals still do rounding, so it doesn't give users accurate arbitrary-precision numbers. A default number format that is much slower than built-in floating point but still subject to unexpected deviation from real arithmetic numbers doesn't seem like a win for users.
- tadfisher 5y ago
  It is impossible to represent all real arithmetic numbers, so it would not be that big a loss.
- int_19h 5y ago
  It gives users rounding that they're used to, from calculators etc. Floats defy common expectations. The fact that we still have to talk about this stuff is exactly the point.
eternityforest 5y ago
So much of computing practice is based on the idea that floats aren't quite real numbers, they're like fuzzy analog voltages almost. Almost nobody thinks about float rounding, they just use something precise enough that it doesn't matter, or use integers. Why break that standard? Everyone expects computer numbers to be just a bit off. If we didn't we would do a lot of stuff differently in incompatible ways. Seems like it would hurt the Python ecosystem if people wrote stuff that assumed floats were perfect decimals, and encouraged code that depends on that. You'd get stuff like serializing to JSON, and reading in some other language with a JSON parser that doesn't know the numbers need to be precise. Plus, it's just faster.

Spivak 5y ago

I mean they switched from strings being bytes of UTF-8 to unicode, never say never for Python 4! It would be a downright Pythonic move.

tzot 5y ago
In CPython 2, a `str` was bytes period; no encoding was enforced, these bytes were not necessarily valid UTF-8, and a `unicode` had either UTF-16 or UTF-32 in-memory representation (decided at compilation time). In CPython 3, a `bytes` is bytes and a `str` has ASCII/UTF-16/UTF-32 in-memory representation (decided at runtime). So CPython 2 strings were not “bytes of UTF-8”, and that is why strings `'\xfc\xf7\xe9'` worked fine, they even printed fine in the proper environments.
- mistrial9 5y ago
  > In CPython 2, a `str` was bytes -- like old C language, a str is really bytes, no encoding is enforced.

amanzi 5y ago

That would suit me too, but not sure of the wider implications.

creata 5y ago

Why do you say that "most of the time... you really want a decimal"? I can't think of any situation where I'd prefer a decimal.Decimal over an ordinary float, except for the textbook example of dollars and cents. In most situations, I'm pretty sure decimal.Decimals would be unacceptably slower.

tomrod 5y ago
In data science, this can be an issue.
samwillis 5y ago
Even with currency now it seems more common to just use ints of the currency’s lowest denomination/subunit (cents, pence etc)
- tadfisher 5y ago
  You might as well use a Decimal at that point, which usually combines an integer mantissa with some inverse exponent of 10. Otherwise you're applying that exponent everywhere you use the value, whether you display it or use it in a mathematical expression.
  - samwillis 5y ago
    I think the advantage of ints over Decimal is interoperability of systems. Anything with a REST api or JSON doesn’t have native support for Decimals, so to use them you have to represent them in component form as an object or as a string. Ints just make that easer at the slight cost at display time. Stripe is a good example of this. > Otherwise you're applying that exponent everywhere you use the value, whether you display it or use it in a mathematical expression. Slightly disagree, I think it’s only when displaying you have to convert to a “human readable” decimal form. They don’t need converting to Decimal for processing. It’s also worth noting there are actually two none decimal currency’s still in use: “Today, only two countries have non-decimal currencies: Mauritania, where 1 ouguiya = 5 khoums, and Madagascar, where 1 ariary = 5 iraimbilanja.” https://en.m.wikipedia.org/wiki/Non-decimal_currency https://en.m.wikipedia.org/wiki/Non-decimal_currency
    - creata 5y ago
      > Anything with a REST api or JSON doesn’t have native support for Decimals This is a very slight nitpick (that might be wrong) but I think it's perfectly in line with the JSON specification to interpret JSON numbers as decimals.

munificent 5y ago

My understanding is that even decimals still do rounding, so it doesn't give users accurate arbitrary-precision numbers. A default number format that is much slower than built-in floating point but still subject to unexpected deviation from real arithmetic numbers doesn't seem like a win for users.

tadfisher 5y ago
It is impossible to represent all real arithmetic numbers, so it would not be that big a loss.
int_19h 5y ago
It gives users rounding that they're used to, from calculators etc. Floats defy common expectations. The fact that we still have to talk about this stuff is exactly the point.

eternityforest 5y ago

So much of computing practice is based on the idea that floats aren't quite real numbers, they're like fuzzy analog voltages almost. Almost nobody thinks about float rounding, they just use something precise enough that it doesn't matter, or use integers. Why break that standard? Everyone expects computer numbers to be just a bit off. If we didn't we would do a lot of stuff differently in incompatible ways. Seems like it would hurt the Python ecosystem if people wrote stuff that assumed floats were perfect decimals, and encouraged code that depends on that. You'd get stuff like serializing to JSON, and reading in some other language with a JSON parser that doesn't know the numbers need to be precise. Plus, it's just faster.