[英]python string index out of range
好。 所以我可能是這個星球上最愚蠢的人,但是有人可以告訴我為什么這會給我一個錯誤(該程序用於使用二等分搜索來搜索按字母順序排列的字符串中的字符):
def isInIter(char, aStr):
print('char :'+char)
print('aStr :'+aStr)
isin = False
while(len(aStr) > 0):
if aStr[len(aStr)/2] == char:
isin = True
break
else:
if aStr[len(aStr)/2] > char:
aStr = aStr[0 : len(aStr)/2]
continue
if aStr[len(aStr)/2] < char:
aStr = aStr[(len(aStr)/2 + 1) :]
continue
return isin
錯誤:
isInIter('d','cddfggjkkqtwyy')
---------------------------------------------------------------------------
IndexError Traceback (most recent call last)
<ipython-input-66-1de0eb4793fd> in <module>()
----> 1 isInIter('d','cddfggjkkqtwyy')
/home/user/Study/Ex/lec5_BisectionSearch.py in isInIter(char, aStr)
5 isin = False
6 while(len(aStr) > 0):
----> 7 if aStr[len(aStr)/2] == char:
8 isin = True
9 break
IndexError: string index out of range
但這按預期工作:
char = raw_input('char :')
aStr = raw_input('aStr :')
isin = False
while(len(aStr) > 0):
if aStr[len(aStr)/2] == char:
isin = True
break
else:
if aStr[len(aStr)/2] > char:
aStr = aStr[0 : len(aStr)/2]
continue
if aStr[len(aStr)/2] < char:
aStr = aStr[len(aStr)/2 + 1 :]
continue
print isin
我感謝您的幫助。
當python經過while循環時,它會等到循環結束以檢查退出條件。 如果壓縮函數,可能會更容易:
def isItIn(streen,carroter):
while len(streen)>0:
if streen[len(streen)/2]==carroter:
return True
if streen[len(streen)/2]>carroter:
streen=streen[0:len(streen)/2]
if len(streen)==0:return False
if streen[len(streen)/2]<carroter:
streen=streen[len(streen)/2+1:]
print isItIn('asdilk','a')
print isItIn('kdsoe','a')
為什么不使用str.index(sub\\[, start\\[, end\\]\\])
? 您可以打賭它具有優化的實現。
In [1]: s = "cddfggjkkqtwyy"
In [2]: s.index("d")
Out[2]: 1
In [3]: s.index("d") > -1
Out[3]: True
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