更換沒有任何進口或內置函數？

Question

這是一個家庭作業問題。我正在定義一個函數，它接受一個字並用另一個字符替換給定的字符。例如替換（「蛋糕」，「A」，「O」）應該返回「可樂」我曾嘗試

def replace(word,char1,char2): 
    newString = "" 
    for char1 in word: 
     char1 = char2 
     newString+=char1 
    return newString #returns 'oooo' 

和

def replace(word,char1,char2): 
    newString = "" 
    if word[char1]: 
     char1 = char2 
     newString+=char1 
    return newString #TypeError: string indices must be integers, not str 

我假設我第一次嘗試是接近到什麼我想要。我的功能出了什麼問題？

Answer 1

試試這個：

def replace(word,char1,char2): 
    newString = "" 
    for next_char in word:   # for each character in the word 
     if next_char == char1:  # if it is the character you want to replace 
      newString += char2  # add the new character to the new string 
     else:      # otherwise 
      newString += next_char # add the original character to the new string 
    return newString 

雖然在Python中已經有做這個的方法：

print "cake".replace("a", "o") 

Answer 2

def replace(word, ch1, ch2) : 
    return ''.join([ch2 if i == ch1 else i for i in word])