有没有人可以帮助我在Python程序中找到错误

问题描述

在我的程序中， 如果我删除return-1语句，我会得到正确的答案，但否则它会一直返回-1。它为什么一直这样做？



我尝试过：

In my program, if I delete the return-1 statement I get the right answer but otherwise it keeps returning -1. Why does it keep doing so?

What I have tried:

def findNextOpr(txt):
    #txt must be a nonempty string. 
    if len(txt)<=0 or not isinstance(txt,str):
        print("type error: findNextOpr")
        return "type error: findNextOpr"
    #In this exercise +, -, *, / are all the 4 operators
    #The function returns -1 if there is no operator in txt,
    #otherwise returns the position of the leftmost operator
    #--- continue the rest of the code here ----#
    op=['+','-','*','/']
    for i in range(len(txt)):
        if txt[i] in op:
            return(i)
        else:
            return(-1)
            
        
        
print(findNextOpr("1+2+3"))

推荐答案

引用：

在我的程序中，如果我删除t他返回1声明我得到正确的答案，但否则它会一直返回-1。为什么会一直这样做？

In my program, if I delete the return-1 statement I get the right answer but otherwise it keeps returning -1. Why does it keep doing so?

因为如果第一个字母不是运算符，这个代码就会得到-1。

试试

Because with this code you get -1 if first letter is not an operator.
Try

def findNextOpr(txt):
    #txt must be a nonempty string. 
    if len(txt)<=0 or not isinstance(txt,str):
        print("type error: findNextOpr")
        return "type error: findNextOpr"
    #In this exercise +, -, *, / are all the 4 operators
    #The function returns -1 if there is no operator in txt,
    #otherwise returns the position of the leftmost operator
    #--- continue the rest of the code here ----#
    op=['+','-','*','/']
    for i in range(len(txt)):
        if txt[i] in op:
            return(i)
        
    return(-1)
            
        
        
print(findNextOpr("1+2+3"))

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