6 ms·

String interpolation isn't a new feature, you are confused. Python just got one more way of doing string interpolation.

by rantanplan 10y ago

TAForObvReasons 10y ago
printf-style specifiers and substitutions, like in the examples GP provided, aren't considered string interpolation.
- rantanplan 10y ago
  > "My name is {name} and I am {age} years old".format(name=name, age=age) This is a textbook example of string interpolation. You can look it up on wikipedia. I am not sure what you mean.
  - TAForObvReasons 10y ago
    The wikipedia examples are somewhat misleading. The string "My name is {name} and I am {age} years old" is a plain string. By itself, there is no interpolation: >>> x = "My name is {name} and I am {age} years old" >>> x 'My name is {name} and I am {age} years old' The format function is what confers meaning. This is identical to a standard printf situation, wherein the string "%d %x" encodes a transformation but in and of itself isn't a transformation. Contrast with the proposal for f-strings: >>> x = f"My name is {name} and I am {age} years old" # this is an error unless name and age are defined The literal mandates a particular interpretation, and the f-string cannot exist outside of that in the same way that the standard string does. Or as the PEP puts it: > It should be noted that an f-string is really an expression evaluated at run time, not a constant value.
    - rantanplan 10y ago
      By itself there's no interpolation, which simply means it's not an expression. But when you do: "{foo} {bar}" % {"foo": "blah", "bar": "blooh"}, this is string interpolation. Is there a definition, anywhere(even a book would suffice), where it has your strict definition of what interpolation is? I'm not trying to undermine the usefulness of the interpolated expressions and what you said. I just really want to know if the definition is so strict. UPDATE: http://rosettacode.org/wiki/String_interpolation_(included) http://rosettacode.org/wiki/String_interpolation_(included) I think that you are the one who's making the definition so specific and strict. I can't find a single source on the Internet that agrees with your definition.
      - actsasbuffoon 10y ago
        Reading the text of the Wikipedia article, I think it does make a distinction between the two styles. string interpolation is the process of evaluating a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values. I read this as saying that the evaluation of the string literal yields a string where the substitution has already been made. That's not the case with the format style of "string interpolation." You provide a template string and call a function with some arguments, and that replaces the placeholders. The string literal does not handle the substitutions itself. I believe the Wikipedia article agrees that this is the deciding factor. A few sentences later, the article includes this statement: Some languages do not offer string interpolation, instead offering a standard function where one parameter is the printf format string, and other(s) provide the values for each placeholder. This sounds pretty similar to what was in Python prior to this release (especially if you know how methods work in Python). Also notice how the statement begins by saying that not all languages offer string interpolation. I think that's the final nail in the coffin of the argument. You could use virtually any language to write a function that handles substitutions in template strings. If that qualified as string interpolation then every language would have it. Since some languages do not, I think we can safely say that we're talking about a syntax feature.
douchescript 10y ago
Dont worry :) soon the other ways will be deprecated. There can be only one _pythonic_ way to do it.
soperj 10y ago
I remember when I started python that one of the big differences was that there wasn't a 1000 ways to do something, but one right way.
- stuaxo 10y ago
  Yup, we could do with a python4 to clean things up ...
- actuallyalys 10y ago
  To be fair, string interpolation is an outlier. Also, Python 3 cleaned up a few areas where there were redundant ways to do something, like standard library modules that had both C and (pure) Python versions.
- amyjess 10y ago
  There's always been multiple ways to do something in Python, just one best way, and the best way has been known to change between versions. See: list comprehensions obsoleting most uses of map() and filter(), then generator expressions obsoleting any uses of list comprehensions that don't need a list object Here's four ways to do the same thing. Naïve way: foo = [] for x in bar: if meets_some_condition(x): foo.append(transform(x)) do_something_with(foo) With map/filter: do_something_with(map(transform, filter(meets_some_condition, bar))) With list comprehensions: do_something_with([transform(x) for x in bar if meets_some_condition(x)]) With generator expressions: do_something_with(transform(x) for x in bar if meets_some_condition(x)) All four of those are valid in modern Python, but the latter and only the latter is the right way to do it. Before Python 2.0, either map/filter or the naïve way was the right way (TBH, I'm not familiar with what was considered right in the old days). When Python 2.0 came out, list comprehensions became the right way. When Python 2.4 came out, generator expressions became the right way. The right way depends on your version of Python. Or for that matter, look at old-style classes vs. new-style classes. When new-style classes came out, they immediately became the one and only right way to do classes, but old style classes still stuck around for the rest of the 2.x series.
  - cookiecaper 10y ago
deleted 10y ago
[deleted]
cstrahan 10y ago
I believe that, when most people say "string interpolation", they mean "first class string interpolation syntax", as opposed to the use of function invocation. I don't have citations, but I hope this perspective helps in some way.

String interpolation isn't a new feature, you are confused. Python just got one more way of doing string interpolation.

TAForObvReasons 10y ago

printf-style specifiers and substitutions, like in the examples GP provided, aren't considered string interpolation.

rantanplan 10y ago
> "My name is {name} and I am {age} years old".format(name=name, age=age) This is a textbook example of string interpolation. You can look it up on wikipedia. I am not sure what you mean.
- TAForObvReasons 10y ago
  The wikipedia examples are somewhat misleading. The string "My name is {name} and I am {age} years old" is a plain string. By itself, there is no interpolation: >>> x = "My name is {name} and I am {age} years old" >>> x 'My name is {name} and I am {age} years old' The format function is what confers meaning. This is identical to a standard printf situation, wherein the string "%d %x" encodes a transformation but in and of itself isn't a transformation. Contrast with the proposal for f-strings: >>> x = f"My name is {name} and I am {age} years old" # this is an error unless name and age are defined The literal mandates a particular interpretation, and the f-string cannot exist outside of that in the same way that the standard string does. Or as the PEP puts it: > It should be noted that an f-string is really an expression evaluated at run time, not a constant value.
  - rantanplan 10y ago
    By itself there's no interpolation, which simply means it's not an expression. But when you do: "{foo} {bar}" % {"foo": "blah", "bar": "blooh"}, this is string interpolation. Is there a definition, anywhere(even a book would suffice), where it has your strict definition of what interpolation is? I'm not trying to undermine the usefulness of the interpolated expressions and what you said. I just really want to know if the definition is so strict. UPDATE: http://rosettacode.org/wiki/String_interpolation_(included) http://rosettacode.org/wiki/String_interpolation_(included) I think that you are the one who's making the definition so specific and strict. I can't find a single source on the Internet that agrees with your definition.
    - actsasbuffoon 10y ago
      Reading the text of the Wikipedia article, I think it does make a distinction between the two styles. string interpolation is the process of evaluating a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values. I read this as saying that the evaluation of the string literal yields a string where the substitution has already been made. That's not the case with the format style of "string interpolation." You provide a template string and call a function with some arguments, and that replaces the placeholders. The string literal does not handle the substitutions itself. I believe the Wikipedia article agrees that this is the deciding factor. A few sentences later, the article includes this statement: Some languages do not offer string interpolation, instead offering a standard function where one parameter is the printf format string, and other(s) provide the values for each placeholder. This sounds pretty similar to what was in Python prior to this release (especially if you know how methods work in Python). Also notice how the statement begins by saying that not all languages offer string interpolation. I think that's the final nail in the coffin of the argument. You could use virtually any language to write a function that handles substitutions in template strings. If that qualified as string interpolation then every language would have it. Since some languages do not, I think we can safely say that we're talking about a syntax feature.

douchescript 10y ago

Dont worry :) soon the other ways will be deprecated. There can be only one _pythonic_ way to do it.

soperj 10y ago

I remember when I started python that one of the big differences was that there wasn't a 1000 ways to do something, but one right way.

stuaxo 10y ago
Yup, we could do with a python4 to clean things up ...
actuallyalys 10y ago
To be fair, string interpolation is an outlier. Also, Python 3 cleaned up a few areas where there were redundant ways to do something, like standard library modules that had both C and (pure) Python versions.
amyjess 10y ago
There's always been multiple ways to do something in Python, just one best way, and the best way has been known to change between versions. See: list comprehensions obsoleting most uses of map() and filter(), then generator expressions obsoleting any uses of list comprehensions that don't need a list object Here's four ways to do the same thing. Naïve way: foo = [] for x in bar: if meets_some_condition(x): foo.append(transform(x)) do_something_with(foo) With map/filter: do_something_with(map(transform, filter(meets_some_condition, bar))) With list comprehensions: do_something_with([transform(x) for x in bar if meets_some_condition(x)]) With generator expressions: do_something_with(transform(x) for x in bar if meets_some_condition(x)) All four of those are valid in modern Python, but the latter and only the latter is the right way to do it. Before Python 2.0, either map/filter or the naïve way was the right way (TBH, I'm not familiar with what was considered right in the old days). When Python 2.0 came out, list comprehensions became the right way. When Python 2.4 came out, generator expressions became the right way. The right way depends on your version of Python. Or for that matter, look at old-style classes vs. new-style classes. When new-style classes came out, they immediately became the one and only right way to do classes, but old style classes still stuck around for the rest of the 2.x series.
- cookiecaper 10y ago

deleted 10y ago

[deleted]

cstrahan 10y ago

I believe that, when most people say "string interpolation", they mean "first class string interpolation syntax", as opposed to the use of function invocation. I don't have citations, but I hope this perspective helps in some way.