Benchmark try/except vs. conditionals for caching (long-lived objects)

try_except_vs_cond.py

#!/usr/bin/env python

import timeit


class Foo:
    base_url = "http://boo"

    def __str__(self):
        try:
            return self._str
        except AttributeError:
            clsname = type(self).__name__
            self._str = f"{clsname}({self.base_url!r})"
            return self._str


class Bar:
    base_url = "http://boo"

    def __str__(self):
        if hasattr(self, "_str"):
            return self._str

        clsname = type(self).__name__
        self._str = f"{clsname}({self.base_url!r})"
        return self._str


class Baz:
    base_url = "http://boo"

    def __str__(self):
        if not hasattr(self, "_str"):
            clsname = type(self).__name__
            self._str = f"{clsname}({self.base_url!r})"
        return self._str


foo = Foo()
bar = Bar()
baz = Baz()

print("foo:", timeit.Timer(stmt="str(foo)", globals=locals()).timeit())
print("bar:", timeit.Timer(stmt="str(bar)", globals=locals()).timeit())
print("baz:", timeit.Timer(stmt="str(baz)", globals=locals()).timeit())