Python For Loop不被感知？

我正試圖製作一個程序，以克每摩爾爲一個化合物的質量。應該很簡單，但我的for循環之一不是像它應該運行（對於範圍內的x（0，var-1））。它不是從0到var-1的整數運行，而是將x保持爲0.是否有人可以看看？非常感謝！Python For Loop不被感知？

代碼如下：

#Set all elements and their mass per mole (up to Xenon) 
elements = [['H' , 1.0079] , ['He' , 4.0026] , ['Li' , 6.941] , ['Be' , 9.0122] , ['B' , 10.811] , ['C' , 12.011] , ['N' , 14.007] , ['O' , 15.999] , ['F' , 18.998] , ['Ne' , 20.180] , ['Na' , 22.990] , ['Mg' , 24.305] , ['Al' , 26.982] , ['Si' , 28.086] , ['P' , 30.974] , ['S' , 32.066] , ['Cl' , 35.453] , ['Ar' , 39.948] , ['K' , 39.098] , ['Ca' , 40.078] , ['Sc' , 44.956] , ['Ti' , 47.88] , ['V' , 50.942] , ['Cr' , 51.996] , ['Mn' , 54.938] , ['Fe' , 55.847] , ['Co' , 58.933] , ['Ni' , 58.693] , ['Cu' , 63.546] , ['Zn' , 65.39] , ['Ga' , 69.723] , ['Ge' , 72.61] , ['As' , 74.922] , ['Se' , 78.96] , ['Br' , 79.904] , ['Kr' , 83.80] , ['Rb' , 85.468] , ['Sr' , 87.62] , ['Y' , 88.906] , ['Zr' , 91.224] , ['Nb' , 92.906] , ['Mo' , 95.94] , ['Tc' , 97.907] , ['Ru' , 101.07] , ['Rh' , 102.91] , ['Pd' , 106.42] , ['Ag' , 107.87] , ['Cd' , 112.41] , ['In' , 114.82] , ['Sn' , 118.71] , ['Sb' , 121.76] , ['Te' , 127.60] , ['I' , 126.90] , ['Xe' , 131.29]] 

#Start the main loop 
while True: 
    grams = 0 
    numOfDistElements = int(input("How many distinct elements?\n")) 

    #Run through all distinct elements in compound 
    #x below is not increasing; stays at 0??? 
    for x in range(0 , numOfDistElements - 1): 
     element = str(input("What is the element?\n")) 
     numOfIndivElements = int(input("How many?\n")) 

     #Check if enterred element is a valid element 
     for y in elements: 
      if y[1] == element: 

       #Add that element's weight to total mass 
       grams += y[2] * numOfIndivElements 

      print(grams)

來源

2017-02-19 AceTrainerMagnus

你怎麼知道'x'沒有改變？你甚至不使用這個值。請在for循環中打印'x'，併爲元素數量輸入> 2的值。 – Matthias

這表明您在提示輸入時輸入了兩個數字。 – ForceBru

陣列被索引分別從0更改您的y[1]和y[2]到y[0]和y[1]開始。

此外，range（）不包含上限。所以，該行應該是簡單的

for x in range(0 , numOfDistElements):

來源

2017-02-19 20:13:58

更具體一些，'if y [1] == element'檢查總是失敗，因爲它比較了'element'和'float'（所以它實際上不能成功），這也是爲什麼潛在的'當檢查'y [2]'時沒有出現IndexError'。 –

我會推薦使用字典，而不是一個列表。而且，你的目標可以用一些邏輯來完成，而不是讓用戶告訴你有多少元素。

#Set all elements and their mass per mole (up to Xenon) 
elements = [['H' , 1.0079] , ['He' , 4.0026] , ['Li' , 6.941] , ['Be' , 9.0122] , ['B' , 10.811] , ['C' , 12.011] , ['N' , 14.007] , ['O' , 15.999] , ['F' , 18.998] , ['Ne' , 20.180] , ['Na' , 22.990] , ['Mg' , 24.305] , ['Al' , 26.982] , ['Si' , 28.086] , ['P' , 30.974] , ['S' , 32.066] , ['Cl' , 35.453] , ['Ar' , 39.948] , ['K' , 39.098] , ['Ca' , 40.078] , ['Sc' , 44.956] , ['Ti' , 47.88] , ['V' , 50.942] , ['Cr' , 51.996] , ['Mn' , 54.938] , ['Fe' , 55.847] , ['Co' , 58.933] , ['Ni' , 58.693] , ['Cu' , 63.546] , ['Zn' , 65.39] , ['Ga' , 69.723] , ['Ge' , 72.61] , ['As' , 74.922] , ['Se' , 78.96] , ['Br' , 79.904] , ['Kr' , 83.80] , ['Rb' , 85.468] , ['Sr' , 87.62] , ['Y' , 88.906] , ['Zr' , 91.224] , ['Nb' , 92.906] , ['Mo' , 95.94] , ['Tc' , 97.907] , ['Ru' , 101.07] , ['Rh' , 102.91] , ['Pd' , 106.42] , ['Ag' , 107.87] , ['Cd' , 112.41] , ['In' , 114.82] , ['Sn' , 118.71] , ['Sb' , 121.76] , ['Te' , 127.60] , ['I' , 126.90] , ['Xe' , 131.29]] 
dict = {} 
for item in elements: 
    dict[item[0]] = item[1] 

string = input("Enter the compound ") 
i = 0 
grams = 0 
while i<len(string): 
    one_letter = string[i] 
    two_letters = string[i:i+2] 

    #check two letters first, since He should be recognized before H 
    if two_letters in dict: 
     #check for number following element, as in H2O 
     if i+2<len(string): 
      if string[i+2].isdigit(): #digit follows element 
       grams += dict[two_letters]*eval(string[i+2]) 
       i +=3 
       continue 
      else: #No digit, element is a single 
       grams += dict[two_letters] 
       i += 2 
       continue 
     else: #no room for a digit after the element; string isn't long enough 
      grams += dict[two_letters] 
      i += 2 
      continue 

    elif one_letter in dict: 
     if i+1<len(string): 
      if string[i+1].isdigit(): #digit follows element 
       grams += dict[one_letter]*eval(string[i+1]) 
       i +=2 
       continue 
      else: 
       grams += dict[one_letter] 
       i += 1 
       continue 
     else: #no room for a digit after the element; string isn't long enough 
      grams += dict[one_letter] 
      i += 1 
      continue 
    else: 
     print("Invalid compound") 
     break 

print(grams)

來源

2017-02-19 20:39:21

Python For Loop不被感知？

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