Python新手自制字符串替换函数异常：输入shyer未输出预期结果

问题原因 #

你的First_Replace函数最后一段的while循环存在死循环问题：
当输入"shyer"时，匹配位置s=1，len(part)=2，所以循环初始i=1+2=3。进入循环后，代码只执行new_word += word[i]，但没有对i进行递增操作，导致i始终等于3，循环条件i < len(word)（此时len(word)=5，3<5永远成立），程序陷入死循环，无法继续执行到输出步骤。

修复后的代码 #

只需要在while循环内添加i += 1即可解决：

word = input("Enter a string : ")

def Ino_String(word,part):
    # if part is in word s will indicate the position where the starting position of part is in word
    # if not s will stay -1
    s = -1

    i = 0
    j = 0
    count = 0
    while i < len(word):
        if word[i] == part[j]:
            count += 1
            j += 1
            i += 1
        else:
            count = 0
            i = i - j + 1
            j = 0
        if count == len(part):
            s = i - len(part)
            break
    return s

def  First_Replace(word,  part, new_part):
    s = Ino_String(word, part)
    if s != -1 :
        new_word = ""
        for i in range(s):
            new_word += word[i]
        for i in range(0, len(new_part)):
            new_word += new_part[i]
        i = s + len(part)
        while i < len(word):
            new_word += word[i]
            i += 1  # 添加这一行，让循环变量递增
    else:
        new_word = "Error: the part you want to replace is not in the string"
    return new_word

print(str(Ino_String(word,"hy")))
new_word = First_Replace(word, 'hy', "how")
print(new_word)

测试验证 #

输入"shyer"时，现在会正常输出1和shower，符合预期。

内容的提问来源于stack exchange，提问作者Moha Med