Is there a Python equivalent to Ruby’s string interpolation?

The Question :

351 people think this question is useful

Ruby example:

name = "Spongebob Squarepants"
puts "Who lives in a Pineapple under the sea? \n#{name}."

The successful Python string concatenation is seemingly verbose to me.

The Question Comments :

The Answer 1

424 people think this answer is useful

Python 3.6 will add literal string interpolation similar to Ruby’s string interpolation. Starting with that version of Python (which is scheduled to be released by the end of 2016), you will be able to include expressions in “f-strings”, e.g.

name = "Spongebob Squarepants"
print(f"Who lives in a Pineapple under the sea? {name}.")

Prior to 3.6, the closest you can get to this is

name = "Spongebob Squarepants"
print("Who lives in a Pineapple under the sea? %(name)s." % locals())

The % operator can be used for string interpolation in Python. The first operand is the string to be interpolated, the second can have different types including a “mapping”, mapping field names to the values to be interpolated. Here I used the dictionary of local variables locals() to map the field name name to its value as a local variable.

The same code using the .format() method of recent Python versions would look like this:

name = "Spongebob Squarepants"
print("Who lives in a Pineapple under the sea? {name!s}.".format(**locals()))

There is also the string.Template class:

tmpl = string.Template("Who lives in a Pineapple under the sea? $name.")
print(tmpl.substitute(name="Spongebob Squarepants"))

The Answer 2

145 people think this answer is useful

Since Python 2.6.X you might want to use:

"my {0} string: {1}".format("cool", "Hello there!")

The Answer 3

32 people think this answer is useful

I’ve developed the interpy package, that enables string interpolation in Python.

Just install it via pip install interpy. And then, add the line # coding: interpy at the beginning of your files!

Example:

#!/usr/bin/env python
# coding: interpy

name = "Spongebob Squarepants"
print "Who lives in a Pineapple under the sea? \n#{name}."

The Answer 4

28 people think this answer is useful

Python’s string interpolation is similar to C’s printf()

If you try:

name = "SpongeBob Squarepants"
print "Who lives in a Pineapple under the sea? %s" % name

The tag %s will be replaced with the name variable. You should take a look to the print function tags: http://docs.python.org/library/functions.html

The Answer 5

28 people think this answer is useful

String interpolation is going to be included with Python 3.6 as specified in PEP 498. You will be able to do this:

name = 'Spongebob Squarepants'
print(f'Who lives in a Pineapple under the sea? \n{name}')

Note that I hate Spongebob, so writing this was slightly painful. 🙂

The Answer 6

4 people think this answer is useful

You can also have this

name = "Spongebob Squarepants"
print "Who lives in a Pineapple under the sea? \n{name}.".format(name=name)

http://docs.python.org/2/library/string.html#formatstrings

The Answer 7

3 people think this answer is useful
import inspect
def s(template, **kwargs):
    "Usage: s(string, **locals())"
    if not kwargs:
        frame = inspect.currentframe()
        try:
            kwargs = frame.f_back.f_locals
        finally:
            del frame
        if not kwargs:
            kwargs = globals()
    return template.format(**kwargs)

Usage:

a = 123
s('{a}', locals()) # print '123'
s('{a}') # it is equal to the above statement: print '123'
s('{b}') # raise an KeyError: b variable not found

PS: performance may be a problem. This is useful for local scripts, not for production logs.

Duplicated:

The Answer 8

2 people think this answer is useful

For old Python (tested on 2.4) the top solution points the way. You can do this:

import string

def try_interp():
    d = 1
    f = 1.1
    s = "s"
    print string.Template("d: $d f: $f s: $s").substitute(**locals())

try_interp()

And you get

d: 1 f: 1.1 s: s

The Answer 9

1 people think this answer is useful

Python 3.6 and newer have literal string interpolation using f-strings:

name='world'
print(f"Hello {name}!")

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