Performance of Various Methods to Test for a Palindrome [Python]
Today, I was fooling around with a couple of programming puzzles. Faced with the task of testing a string to see whether or not it is a palindrome, I conceived of several ways t
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Use the timeit module for speed-testing, the profile module for performance statistics, and the dis module for bytecode disassembly.
The script below demonstrates how the modules can be used.
One thing to notice from the output is how much the number of function calls can affect the overall performance (and, of course, the same thing goes for the number of bytecode instructions).
Hopefully, that (and a little more experimentation) should give you enough clues on how to improve the efficiency of your functions.
from timeit import timeit from cProfile import runctx from dis import dis def analyse(*args): victim = 'detartrated' number = 1000 for func in args: print('\n%s\n' % ('#' * 50)) name = func.__name__ print('test: %s(%r): %r' % (name, victim, func(victim))) code = '%s(%r)' % (name, victim) duration = timeit( code, 'from __main__ import %s' % name, number=number) usec = 1000000 * duration / number print('time: %s: %.2f usec/pass\n' % (code, usec)) runctx(code, globals(), locals()) dis(func) def check_palin1(victim): """ check progressively inner chars """ x = 0 # len/2 is num of iter needed for guarantee while x < (len(victim)/2): # on pass n, compare nth letter and nth to last letter if victim[x+0] is victim[-(1+x)]: # then increment the n counter x += 1 else: return False return True def check_palin2(victim): """ check first and last chars repeatedly """ tmp = [] for i in victim: # convert string into list tmp.append(i) # if 1 or 0 char left, palin is guaranteed while len(tmp) > 1: # if the first and last characters are the same letter if tmp[0] is tmp[-1]: # remove them both tmp.pop(0) tmp.pop(-1) else: return False return True def check_palin3(victim): """ reverse string and compare to original using a loop """ tmp = "" # for every letter for i in victim: # cat it to the beginning, not append tmp = i + tmp return tmp == victim def check_palin4(victim): """ reverse string and compare to original using slice syntax """ return victim == victim[::-1] analyse(check_palin1, check_palin2, check_palin3, check_palin4)Output:
################################################## test: check_palin1('detartrated'): True time: check_palin1('detartrated'): 3.80 usec/pass 9 function calls in 0.000 seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 0.000 0.000:1( ) 1 0.000 0.000 0.000 0.000 test.py:20(check_palin1) 6 0.000 0.000 0.000 0.000 {len} 1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 22 0 LOAD_CONST 1 (0) 3 STORE_FAST 1 (x) 24 6 SETUP_LOOP 72 (to 81) >> 9 LOAD_FAST 1 (x) 12 LOAD_GLOBAL 0 (len) 15 LOAD_FAST 0 (victim) 18 CALL_FUNCTION 1 21 LOAD_CONST 2 (2) 24 BINARY_DIVIDE 25 COMPARE_OP 0 (<) 28 POP_JUMP_IF_FALSE 80 26 31 LOAD_FAST 0 (victim) 34 LOAD_FAST 1 (x) 37 LOAD_CONST 1 (0) 40 BINARY_ADD 41 BINARY_SUBSCR 42 LOAD_FAST 0 (victim) 45 LOAD_CONST 3 (1) 48 LOAD_FAST 1 (x) 51 BINARY_ADD 52 UNARY_NEGATIVE 53 BINARY_SUBSCR 54 COMPARE_OP 8 (is) 57 POP_JUMP_IF_FALSE 73 28 60 LOAD_FAST 1 (x) 63 LOAD_CONST 3 (1) 66 INPLACE_ADD 67 STORE_FAST 1 (x) 70 JUMP_ABSOLUTE 9 30 >> 73 LOAD_GLOBAL 1 (False) 76 RETURN_VALUE 77 JUMP_ABSOLUTE 9 >> 80 POP_BLOCK 31 >> 81 LOAD_GLOBAL 2 (True) 84 RETURN_VALUE ################################################## test: check_palin2('detartrated'): True time: check_palin2('detartrated'): 10.57 usec/pass 30 function calls in 0.000 seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 0.000 0.000 :1( ) 1 0.000 0.000 0.000 0.000 test.py:33(check_palin2) 6 0.000 0.000 0.000 0.000 {len} 11 0.000 0.000 0.000 0.000 {method 'append' of 'list' objects} 1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 10 0.000 0.000 0.000 0.000 {method 'pop' of 'list' objects} 35 0 BUILD_LIST 0 3 STORE_FAST 1 (tmp) 36 6 SETUP_LOOP 27 (to 36) 9 LOAD_FAST 0 (victim) 12 GET_ITER >> 13 FOR_ITER 19 (to 35) 16 STORE_FAST 2 (i) 38 19 LOAD_FAST 1 (tmp) 22 LOAD_ATTR 0 (append) 25 LOAD_FAST 2 (i) 28 CALL_FUNCTION 1 31 POP_TOP 32 JUMP_ABSOLUTE 13 >> 35 POP_BLOCK 40 >> 36 SETUP_LOOP 75 (to 114) >> 39 LOAD_GLOBAL 1 (len) 42 LOAD_FAST 1 (tmp) 45 CALL_FUNCTION 1 48 LOAD_CONST 1 (1) 51 COMPARE_OP 4 (>) 54 POP_JUMP_IF_FALSE 113 42 57 LOAD_FAST 1 (tmp) 60 LOAD_CONST 2 (0) 63 BINARY_SUBSCR 64 LOAD_FAST 1 (tmp) 67 LOAD_CONST 3 (-1) 70 BINARY_SUBSCR 71 COMPARE_OP 8 (is) 74 POP_JUMP_IF_FALSE 106 44 77 LOAD_FAST 1 (tmp) 80 LOAD_ATTR 2 (pop) 83 LOAD_CONST 2 (0) 86 CALL_FUNCTION 1 89 POP_TOP 45 90 LOAD_FAST 1 (tmp) 93 LOAD_ATTR 2 (pop) 96 LOAD_CONST 3 (-1) 99 CALL_FUNCTION 1 102 POP_TOP 103 JUMP_ABSOLUTE 39 47 >> 106 LOAD_GLOBAL 3 (False) 109 RETURN_VALUE 110 JUMP_ABSOLUTE 39 >> 113 POP_BLOCK 48 >> 114 LOAD_GLOBAL 4 (True) 117 RETURN_VALUE ################################################## test: check_palin3('detartrated'): True time: check_palin3('detartrated'): 2.77 usec/pass 3 function calls in 0.000 seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 0.000 0.000 :1( ) 1 0.000 0.000 0.000 0.000 test.py:50(check_palin3) 1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 52 0 LOAD_CONST 1 ('') 3 STORE_FAST 1 (tmp) 54 6 SETUP_LOOP 24 (to 33) 9 LOAD_FAST 0 (victim) 12 GET_ITER >> 13 FOR_ITER 16 (to 32) 16 STORE_FAST 2 (i) 56 19 LOAD_FAST 2 (i) 22 LOAD_FAST 1 (tmp) 25 BINARY_ADD 26 STORE_FAST 1 (tmp) 29 JUMP_ABSOLUTE 13 >> 32 POP_BLOCK 57 >> 33 LOAD_FAST 1 (tmp) 36 LOAD_FAST 0 (victim) 39 COMPARE_OP 2 (==) 42 RETURN_VALUE ################################################## test: check_palin4('detartrated'): True time: check_palin4('detartrated'): 0.65 usec/pass 3 function calls in 0.000 seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 0.000 0.000 :1( ) 1 0.000 0.000 0.000 0.000 test.py:59(check_palin4) 1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 61 0 LOAD_FAST 0 (victim) 3 LOAD_FAST 0 (victim) 6 LOAD_CONST 1 (None) 9 LOAD_CONST 1 (None) 12 LOAD_CONST 2 (-1) 15 BUILD_SLICE 3 18 BINARY_SUBSCR 19 COMPARE_OP 2 (==) 22 RETURN_VALUE
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