Python Can'；t在函数中创建数组

当我运行下面的代码时，我希望变量“a”包含192.168.1.1-192.168.1.254之间的IP列表，但当我运行“print（dir（a[：]）”时，它抛出错误：

错误：

["[IPv4Address('192.168.1.254')]"]
Traceback (most recent call last):
  File "./test.py", line 27, in <module>
    print(dir(a[:]))
TypeError: 'NoneType'

    python3
    import ipaddress
    import csv

used_ips = []

def csv_dict_reader(file_obj):
    """
    Read a CSV file using csv.DictReader
    """
    reader = csv.DictReader(file_obj, delimiter=',')
    for line in reader:
       used_ips.append(line["ip_address"])
       print(used_ips)

def ip_list(network_addr):
   ips = []
   addr = ipaddress.ip_network(network_addr)
   for i in addr.hosts():
      ips.append([i])

if __name__ == "__main__":
    with open("data.csv") as f_obj:
        csv_dict_reader(f_obj)

a = ip_list('192.168.1.0/24')
print(dir(a[:]))

---

在ip_列表的末尾返回ip

python3
import ipaddress
import csv

used_ips = []

def csv_dict_reader(file_obj):
    """
    Read a CSV file using csv.DictReader
    """
    reader = csv.DictReader(file_obj, delimiter=',')
    for line in reader:
       used_ips.append(line["ip_address"])
       print(used_ips)

def ip_list(network_addr):
   ips = []
   addr = ipaddress.ip_network(network_addr)
   for i in addr.hosts():
      ips.append([i])
   return ips

if __name__ == "__main__":
    with open("data.csv") as f_obj:
        csv_dict_reader(f_obj)

a = ip_list('192.168.1.0/24')
print(dir(a[:]))