advanced string formatting vs template strings

Question

I was wondering if there is a advantage of using template strings instead of the new advanced string formatting?

Answer 1

One key advantage of string templates is that you can substitute only some of the placeholders using the safe_substitute method. Normal format strings will raise an error if a placeholder is not passed a value. For example:

"Hello, {first} {last}".format(first='Joe')

raises:

Traceback (most recent call last):
  File "", line 1, in 
KeyError: 'last'

But:

from string import Template
Template("Hello, $first $last").safe_substitute(first='Joe')

Produces:

'Hello, Joe $last'

Note that the returned value is a string, not a Template; if you want to substitute the $last you'll need to create a new Template object from that string.