2013-03-28 49 views
1

我做節目得到了一些信件量STR:的Python:最大遞歸深度而獲得一個物體的

def convert(number): 
    lettercount = 0 

    numstr = str(number) 

    # One's places 
    if len(numstr) is 1: 
     if number == 1 or number == 2 or number == 6: 
      lettercount += 3 

     elif number == 4 or number == 5 or number == 9: 
      lettercount += 4 

     else: 
      lettercount += 5 

    # Ten's places 
    elif len(numstr) is 2: 
     if number == 10: 
      lettercount += 3 

     elif number == 11 or number == 12: 
      lettercount += 6 

     elif number == 15 or number == 16: 
      lettercount += 7 

     elif number == 13 or number == 14 or number == 19: 
      lettercount += 8 

     elif number == 17 or number == 18: 
      lettercount += 9 

     elif number == 20 or number == 30 or number == 40 or\ 
      number == 80 or number == 90: 
      lettercount += 6 

     else: 
      lettercount += convert(int((numstr)[-1])) 
      lettercount += convert(int(round(number, -1))) 

    return lettercount 

print "88 has %i letters in its name." % convert(88) 
print "23 has %i letters in its name." % convert(23) 
print "46 has %i letters in its name." % convert(46) 

它工作得很好,並返回88的正確響應和23,但它在46上給出了遞歸深度錯誤。我很困惑;爲什麼只發生在46歲?


固定碼:

def convert(number): 
    lettercount = 0 

    numstr = str(number) 

    # One's places 
    if len(numstr) == 1: 
     if number == 1 or number == 2 or number == 6: 
      lettercount += 3 

     elif number == 4 or number == 5 or number == 9: 
      lettercount += 4 

     else: 
      lettercount += 5 

    # Ten's places 
    elif len(numstr) == 2: 
     if number == 10: 
      lettercount += 3 

     elif number == 40 or number == 50: 
      lettercount += 5 

     elif number == 11 or number == 12 or number == 20 or number == 30 or\ 
      number == 80 or number == 90: 
      lettercount += 6 

     elif number == 15 or number == 16: 
      lettercount += 7 

     elif number == 13 or number == 14 or number == 19: 
      lettercount += 8 

     elif number == 17 or number == 18: 
      lettercount += 9 

     else: 
      lettercount += convert(int((numstr)[-1])) 
      lettercount += convert((int(numstr) // 10) * 10) 

    return lettercount 

print "88 has %i letters in its name." % convert(88) 
print "23 has %i letters in its name." % convert(23) 
print "46 has %i letters in its name." % convert(46) 
+1

因爲'輪(46,-1 )'是'50'。 – JBernardo

+2

提示:不要使用len(numstr)是2',使用'len(numstr)== 2',因爲如果兩個對象在同一個內存點上,'is''只返回'True';如果值相同,'=='返回'True'。 –

+0

@ F3AR3DLEGEND對於像2這樣的簡單整數,'is'測試將始終有效,因爲它是不可變的類型,所以它的所有實例都在相同的內存中。但我同意,只有在想要檢查兩個對象實際上是同一個對象時才應該使用'is'。 – lxop

回答

2

因爲當你做

convert(int(round(number, -1))) 

您呼叫convert(50)。由於您的if語句不涵蓋50,它將再次到達else,並再次調用convert(50),依此類推。

2

這裏的問題是round(46, -1)將產生值50。當convert被稱爲與價值50它會去相同的一行

lettercount += convert(int(round(number, -1))) 

round(50, -1)通話將產生50,並在這一點上convert功能將無限地執行