Issue 28309: Accelerate string.Template by using formatted string literals (original) (raw)

Proposed patch makes string.Template compiling template to formatted string literal. Since for now using formatted string literals is the fastest way of formatting strings, this significantly speeds up Template substitution.

$ ./python -m perf timeit -s 'from string import Template; s = Template("$who likes $what")' -- 's.substitute(who="tim", what="ham")'

Unpatched: Median +- std dev: 46.1 us +- 4.2 us Patched: Median +- std dev: 11.1 us +- 0.5 us

The drawback is that compiling template adds high overhead.

$ ./python -m perf timeit -s 'from string import Template' -- 's = Template("$who likes $what"); s.substitute(who="tim", what="ham")'

Unpatched: Median +- std dev: 51.7 us +- 1.5 us Patched: Median +- std dev: 672 us +- 38 us

The benefit of using compiled templates is achieved only if make at least 20 substitutions with the same template.

Third-party template engines can use the same approach in Python 3.6+.