想知道是哪里错了（Python：已知字符串str ，统计每个字母出现的次数）

 str-' hnustnicandcomputer                                                                                                                       or "license" for more in
 dictl=0                                                                 Traceback (most recent call last):l                                RESTART: C:\Users \healer\Desktop118.py
 for iin str:                                                                    File 'C:\Users \healer\Desktop\18.py"，line1in<module)
      ifi in str:                                                               dictlLiJ=dictilil+1
            dictllij+=1                                                     KeyError:h'
      else:
                                                                Traceback  dictilil=1                                                                                  RESTART: C:\Users \healer\Desktop\18.py
 print(dicti）                                                                             （most recent call last）:  File "C:lUsers \healer\Desktop118.py,line1in<module>
                                                                   dictlliJ=dictilil+1
                                                               KeyError:
                                                                              h
                                                               Ph:
                                                                                                        1    t':l,#:1,"c"l
                                                              Traceback (most recent call last）:                            RESTART: C:\Users Vhealer\Desktop118.py
                                                                  dictlLil+=l