Nick Coghlan: >There's a similar performance glitch associated with constructing a tuple from a generator expression (with vanilla 2.4, detouring via list is actually faster)
You look right: .from time import clock .print "[x for x in l], list(x for x in l), aux = list(x for x in l); tuple(aux), tuple(x for x in l):" .for np in range(13, 21): . n = 1*2**np . print "n:", n, " s:", . l = xrange(n) . t1 = clock() . [x for x in l] . t2 = clock() . print round(t2-t1,3), . . t1 = clock() . list(x for x in l) . t2 = clock() . print round(t2-t1,3), . . t1 = clock() . aux = list(x for x in l) . tuple(aux) . t2 = clock() . print round(t2-t1,3), . . #l = tuple(l) useless . t1 = clock() . tuple(x for x in l) . t2 = clock() . print round(t2-t1,3) Output: [x for x in l], list(x for x in l), aux = list(x for x in l); tuple(aux), tuple(x for x in l): n: 8192 s: 0.01 0.007 0.01 0.013 n: 16384 s: 0.024 0.019 0.021 0.032 n: 32768 s: 0.054 0.042 0.049 0.113 n: 65536 s: 0.111 0.078 0.101 0.088 n: 131072 s: 0.196 0.155 0.183 0.177 n: 262144 s: 0.436 0.385 0.429 1.832 n: 524288 s: 0.921 0.744 0.877 8.271 n: 1048576 s: 1.86 1.546 1.866 33.154 The timings for tuple(x for x in l) seem to grow as len(n)**2. Bear hugs, Bearophile -- http://mail.python.org/mailman/listinfo/python-list
