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Description:

frepr 0.1.1

frepr

Fast float repr() for CPython using
https://github.com/google/double-conversion. Approximately 8X faster than
the built-in function.

Quick Start
>>> import frepr
>>> frepr.frepr(-1.8397892359791307e+134)
'-1.8397892359791307e+134'
>>> from timeit import timeit
>>> timeit('repr(-1.8397892359791307e+134)')
2.7296602272476758
>>> frepr.install()
>>> timeit('repr(-1.8397892359791307e+134)')
0.35723431229251545
>>> frepr.uninstall()

API

frepr.frepr(value)
Returns shortest string representation of a floating point value. The argument
doesn’t have to be a float, as long as it is coercible to one (i.e. it has
a __float__() method).

frepr.install()
Monkey-patches the Python runtime. Subsequent calls to repr() on floats
will use the faster algorithm. This is safe to call multiple times.

frepr.uninstall()
Reverses the monkey-patching done by install(). Subsequent calls to
repr() will use the original built-in algorithm. This is safe to call
multiple times, even if install() was not called first.

Features

On average, approximately 8X faster than the standard function. (This result
obtained on Python 3.6.0 64-bit/Windows 7/Intel Core i3 @ 2.93GHz. Test your
own system with tests/perf.py).
Speeds up the standard json package (and any other library that relies on
repr()).
Output is guaranteed to contain the shortest string of decimal digits
necessary to uniquely identify the original IEEE 754 floating-point value.
Guaranteed to satisfy value == ast.literal_eval(frepr(value)).
Tested on CPython 2.6 through 3.6; probably works on other versions too.

Limitations

Currently, there is no support for alternative Python implementations (e.g.
PyPy).
Output can be slightly different from the native function, due to
floating-point rounding (but see accuracy guarantees above).
Has no effect on other built-in methods of converting floats to strings (e.g.
str(), str.format(), "%f", "%g").

See Also

https://github.com/google/double-conversion - Core algorithm
implementation. This is the same implementation used by Chrome’s V8
JavaScript engine, among others.
https://bugs.python.org/issue12450 - CPython issue from 2011 about this
idea.