import os, threading
def foo(s):
print s
for dir in os.listdir(os.getcwd()):
threading.Thread(target=lambda: foo(dir)).start()
What bug may cause this to print something other than the contents of the current directory?
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9 comments:
I feel like it's too soon to just answer straight out before other people try... how about...
print "Yrg'f fnl bf.yvfgqve(pjq)==['n', 'o']. Ba gur svefg eha guebhtu gur sbe ybbc, qve=='n', naq gur guernq vf fgnegrq. Vs nsgre gur guernq vf fgnegrq, ohg orsber vg trgf gb vaibxr sbb(qve) gur qve inevnoyr vf frg gb 'o' (orpnhfr gur ybbc vf eha gur frpbaq gvzr) gura sbb('o') jvyy or pnyyrq naq lbh'yy frr 'o\\ao\\a'".decode('rot13')
Exactly.
for dir in os.listdir(os.getcwd()):
threading.Thread(target=foo, args=(dir,)).start()
Is the right way to do it ? Then dir would be evaluated at the Thread creation.
That's probably the best way, yes.
There's another common idiom which is doing something like:
lambda dir=dir: foo(dir)
OTOH, in this case there's already a standard way of passing arguments, as shown above.
lamdba is evil.
using threading for output is a friend of lambda.
Harald Armin Massa notonblogger
lambda is GOD!
How else would we say:
total_size = reduce( os.listdir(os.getcwd()), lambda a,x: a+os.stat(x).st_size,0 )
short, clear, and to the point
total_size = sum([ os.stat(x).st_size for x in os.listdir(os.getcwd())])
I like lambda too, but the non-lambda version is much clearer.
Shouldn't the lambda expression close over the current value of dir?
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