Correzione Soluzione Problema 1

def elimalphafor(str):
# @param str : string
# @return string
    rstr=""
    for i in range(0,len(str)):
         c=str[i]
         if not(c.isalpha()):
            rstr=rstr+c
    return rstr

def elimalphawhile(str):
# @param str : string
# @return string
    rstr=""
    i=0
    while i<(len(str)):
          c=str[i]
          if not(c.isalpha()):
            rstr=rstr+c
          i=i+1
    return rstr

def elimdigitfor(str):
# @param str : string
# @return string
    rstr=""
    for i in range(0,len(str)):
         c=str[i]
         if not(c.isdigit()):
            rstr=rstr+c
    return rstr

def elimdigitwhile(str):
# @param str : string
# @return string
    rstr=""
    i=0
    while i<(len(str)):
          c=str[i]
          if not(c.isdigit()):
            rstr=rstr+c
          i=i+1
    return rstr