如何在字符串中找到最左边的数字和/或运算符。该字符串是一个算术表达式。 [英] How do I find the leftmost number and/or operator in a string. The string is an arithmetic expression.

问题描述

假设一个字符串是1 + 2-3 / 4 * 5

如果我将该位置设为2.那么如何返回最左边数字的值2和 - 最左边的运营商



我尝试了什么：



我发现了对于运营商。但是我需要字符串的帮助。

Suppose a string is "1+2-3/4*5"
If I give the position as 2. Then how do I return the value 2 for the leftmost number and - for the leftmost operator

What I have tried:

I have found out for operator. But I need help for string.

op=['+','-','*','/']
    
    for i in range(len(txt)):
        if txt[i] in op:
            return(i)
            break
    else:
        return(-1)

推荐答案

您需要将字符串解析为标记，数字和运算符，然后根据结果进行计算。请参阅字符串以润色表示法 - Google搜索 [ ^ ]

You need to parse the string into tokens, numbers and operators and then do the calculations from the results. See string to polish notation - Google Search[^]

这篇关于如何在字符串中找到最左边的数字和/或运算符。该字符串是一个算术表达式。的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！