list - python generator yield for a file -

i want use generator script alwayse exception:

traceback (most recent call last):   file "scan.py", line 56, in scan_m     line in ip_list:   file "scan", line 46, in expand_ip_addr     yield str(ip) + '\n' unboundlocalerror: local variable 'ip' referenced before assignment 

and here code, should change? had never used generator before.

def expand_ip_addr():     open('ip.txt', 'r') file_in:             #remove blank lines         line in file_in:              if '/' in str(line):                 ip in ipnetwork(str(line)):                     yield str(ip             else:                 line  def scan_m(ip_list):     = 1     try:         line in ip_list:             # line             = + 1   def main():     ip_list = expand_ip_addr()     scan_m(ip_list)  if __name__ == "__main__":     main() 

---

update mistake else statement wrong, sry

change

for line in file_in.read().replace('\n\n', '\n'): 

and

else:     yield str(ip) + '\n' 

to

for line in file_in:     line = line.strip()     if not line: continue 

and

else:     yield line + '\n'