为什么python如下代码中find_index总是执行else语句部分

Question

问题遇到的现象和发生背景

问题相关代码，请勿粘贴截图

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

-- coding: utf-8 --

"""
Created on Sat Mar 5 11:33:51 2022

@author: Administrator
"""

class pxcheck:
def init(self):
pass

def check_exist(self,path,mark):
    if type(path)==str and type(mark)==str:
        decision=mark in path
        print('Is the mark in the path string:',decision)
        return(decision)
    else:
        print('Please input path and mark in string!')
            

def find_index(self,path,mark):
    if type(path)==str and type(mark)==str:
        decision=self.check_exist(path,mark)
        if decision:
            index=0
            index_set=[]
            for each_mark in path:
                index+=1
                if each_mark==mark:
                    temp_index=index-1
                    index_set.append(temp_index)
            return(index_set)
        else:
            print('There is no mark %s here.'%mark)
    else:
        print('Please input path and mark in string!')
    
def check_suffix(self,path):
    if type(path)==str:
        index_set=self.find_index(path,mark='.')
        length=len(index_set)
        index=index_set[length-1]+1
        length1=len(path)
        suffix=path[index:length1]
        return(suffix)

if name=='main':
a=pxcheck()
testpath=r'www.http.xls'
a.find_index(testpath,'.')
testsuffix=a.check_suffix(testpath)

运行结果：a.find_index(testpath,'.')
There is no mark . here.

Answer 1