4 ms·

Does Python have this?

by mofle 15y ago

stdbrouw 15y ago
Don't think so, but I wouldn't want it anyway, the Ruby syntax being as it is. I think the CoffeeScript equivalents are more intuitive: @current_user ?= User.find() # as opposed to @current_user ||= User.find() and @summary = excerpt?.squish # as opposed to @summary &&= excerpt.squish
MostAwesomeDude 15y ago
Python doesn't need it; the savings from not double-evaluating things aren't there. Additionally, Python lore is to expand this idiom to an if statement, for explicitness, especially in polymorphic situations where you actually want to check for "<expr> is None" rather than "bool(<expr>)". Both of these examples are Railsy; equivalent Djangoy statements in form validation would have to deal with None: if data["incoming"] is None: data["incoming"] = "Default value" ... if data["incoming"]: data["incoming"] = data["incoming"].strip() Because of Python's string immutability, there's no point to dodging the assignment; you're still going to incur new string creation anyway.
- mitchty 15y ago
  I'm sort of torn on using these magic operators in Ruby, and i've used ruby since the 1.4 days. For example this: some_var &&= replace_var() some_var ||= initialize_var() versus a more conventional/idiomatic if: some_var = (some_var) ? replace_var() : initialize_var() ||= turns out to be rather useful as a general assign once operator, but i'm having a hard time justifying use of &&=. That and I find myself after learning Erlang to try to assign only once when possible to make debugging easier. While ||= isn't strictly needed, it makes assigning to class/module variables in a single line easier in general. I'm not sure I agree with the Python "always expand to an if statement" methodology though, it just seems like a bit of unneeded yak shaving. (note: i don't use rails so your post may be specific to web frameworks and I'm off my rocker, if so disregard. >.<)

Does Python have this?

by mofle 15y ago

Does Python have this?

Don't think so, but I wouldn't want it anyway, the Ruby syntax being as it is. I think the CoffeeScript equivalents are more intuitive: @current_user ?= User.find() # as opposed to @current_user ||= User.find() and @summary = excerpt?.squish # as opposed to @summary &&= excerpt.squish

MostAwesomeDude 15y ago

Python doesn't need it; the savings from not double-evaluating things aren't there. Additionally, Python lore is to expand this idiom to an if statement, for explicitness, especially in polymorphic situations where you actually want to check for "<expr> is None" rather than "bool(<expr>)". Both of these examples are Railsy; equivalent Djangoy statements in form validation would have to deal with None: if data["incoming"] is None: data["incoming"] = "Default value" ... if data["incoming"]: data["incoming"] = data["incoming"].strip() Because of Python's string immutability, there's no point to dodging the assignment; you're still going to incur new string creation anyway.

mitchty 15y ago
I'm sort of torn on using these magic operators in Ruby, and i've used ruby since the 1.4 days. For example this: some_var &&= replace_var() some_var ||= initialize_var() versus a more conventional/idiomatic if: some_var = (some_var) ? replace_var() : initialize_var() ||= turns out to be rather useful as a general assign once operator, but i'm having a hard time justifying use of &&=. That and I find myself after learning Erlang to try to assign only once when possible to make debugging easier. While ||= isn't strictly needed, it makes assigning to class/module variables in a single line easier in general. I'm not sure I agree with the Python "always expand to an if statement" methodology though, it just seems like a bit of unneeded yak shaving. (note: i don't use rails so your post may be specific to web frameworks and I'm off my rocker, if so disregard. >.<)