On 2/7/2012 4:51 PM, PJ Eby wrote:
One thing I'm a bit worried about is repeated imports, especially ones
that are inside frequently-called functions. In today's versions of
Python, this is a performance win for "command-line tool platform"
systems like Mercurial and PEAK, where you want to delay importing as
long as possible, in case the code that needs the import is never called
at all... but, if it *is* used, you may still need to use it a lot of
times.
When writing that kind of code, I usually just unconditionally import
inside the function, because the C code check for an already-imported
module is faster than the Python "if" statement I'd have to clutter up
my otherwise-clean function with.
importlib could provide a parameterized decorator for functions that are
the only consumers of an import. It could operate much like this:
def imps(mod):
def makewrap(f):
def wrapped(*args, **kwds):
print('first/only call to wrapper')
g = globals()
g[mod] = __import__(mod)
g[f.__name__] = f
f(*args, **kwds)
wrapped.__name__ = f.__name__
return wrapped
return makewrap
@imps('itertools')
def ic():
print(itertools.count)
ic()
ic()
#
first/only call to wrapper
<class 'itertools.count'>
<class 'itertools.count'>
--
Terry Jan Reedy
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