哪个不是python合法标识符

import keyword
import string
def is_valid_py_name(py_name):
 py_name = py_name.strip()
 if keyword.iskeyword(py_name):
 print "'{0}' is a python keyword!".format(py_name)
 return False
 elif py_name == "":
 print "empty input!"
 return False
 elif py_name[0] not in (string.letters+'_'):
 print "'{0}' not start with _ or letter!".format(py_name)
 return False
 else:
 for i in range(1,len(py_name)):
 if py_name[i] not in (string.letters+'_'+string.digits):
 print "'{0}' is invalid letter!".format(py_name[i])
 return False
 print "'{0}' is valid py name!".format(py_name)
 return True
 
if __name__ == "__main__":
 is_valid = False
 while not is_valid:
 print "Please enter a string:"
 py_name = raw_input()
 is_valid = is_valid_py_name(py_name)