str_1='wo shi yi zhi da da niu '
char_1='i'
nPos=str_1.index(char_1)
print(nPos)

str_1='wo shi yi zhi da da niu '
char_1='i'
nPos=str_1.find(char_1)
print(nPos)

#开挂模式
str_1='wo shi yi zhi da da niu '
char_1=str(input('Please input the Char you want:'))
count=0
str_list=list(str_1)
for each_char in str_list:
 count+=1
 if each_char==char_1:
  print(each_char,count-1)

Please input the Char you want:i
i 0
i 1
i 2
i 3