Python 3.6 conversion of NTP server query function

Question

How would you convert Python 2.7 to Python 3.6.5? Here, I am trying to query a set of NTP time servers and determine which one is the outlier.

It is probably a few simple changes but I am unsure..

from contextlib import closing
from socket import socket, AF_INET, SOCK_DGRAM
import sys
import struct
import time

NTP_PACKET_FORMAT = "!12I"
NTP_DELTA = 2208988800L # 1970-01-01 00:00:00
NTP_QUERY = b'\x1b' + 47 * '\0'  

def ntp_time(host="pool.ntp.org", port=123):
    with closing(socket( AF_INET, SOCK_DGRAM)) as s:
        s.sendto(NTP_QUERY, (host, port))
        msg, address = s.recvfrom(1024)
    unpacked = struct.unpack(NTP_PACKET_FORMAT,
            msg[0:struct.calcsize(NTP_PACKET_FORMAT)])
    return unpacked[10] + float(unpacked[11]) / 2**32 - NTP_DELTA

if __name__ == "__main__":
    print time.ctime(ntp_time()).replace("  "," ")

Have you tried running your code on the 3.6.5 interpreter? If so what errors/warnings do you get. The question is much too broad to be answered by anyone on this site. — vividpk21, Aug 30 '18 at 16:42
IMHO this question isn't too broad, but you should also show us your attempt at a Python 3 version, and explain the errors that you get when you try to run it on Python 3.6. The 2to3 tool can help with the conversion, but this code will need a few more tweaks, due to the Python 3 way of handling bytes. — PM 2Ring, Aug 30 '18 at 16:52
Yes, that old long integer format doesn't exist in Python 3. You will need to learn the basic differences between Python 2 & 3 to do this conversion correctly. The 2to3 program should be part of your Python installation, and it can convert stuff like that. You might have a couple of different versions of 2to3, so make sure you run the latest one! — PM 2Ring, Aug 30 '18 at 17:03
After I change print(), I get error, _TypeError: a byte-like object is required, not 'str'_ on.. `s.sendto(NTP_QUERY, (host, port))` & `print time.ctime(ntp_time()).replace(" "," ")` — Hosep, Aug 30 '18 at 17:16

PM 2Ring · Answer 1 · 2018-08-30T20:53:38.523

Here's a version of your code with minimal changes that runs correctly on Python 3.6. Apart from fixing the prints and that long integer literal, which I did automatically using 2to3, I also changed NTP_QUERY to a bytes string.

from contextlib import closing
from socket import socket, AF_INET, SOCK_DGRAM
import sys
import struct
import time

NTP_PACKET_FORMAT = "!12I"
NTP_DELTA = 2208988800 # 1970-01-01 00:00:00
NTP_QUERY = b'\x1b' + bytes(47)

def ntp_time(host="pool.ntp.org", port=123):
    with closing(socket( AF_INET, SOCK_DGRAM)) as s:
        s.sendto(NTP_QUERY, (host, port))
        msg, address = s.recvfrom(1024)
    unpacked = struct.unpack(NTP_PACKET_FORMAT,
            msg[0:struct.calcsize(NTP_PACKET_FORMAT)])
    return unpacked[10] + unpacked[11] / 2**32 - NTP_DELTA

if __name__ == "__main__":
    print(time.ctime(ntp_time()).replace("  "," "))

There are a few more things that can be done to take advantage of Python 3 features. Here's a more streamlined version. We don't need contextlib, since a Python 3 socket can be used directly in a with statement. And we don't need struct, as a Python 3 int has a from_bytes method.

from socket import socket, AF_INET, SOCK_DGRAM
import time

NTP_DELTA = 2208988800 # 1970-01-01 00:00:00
NTP_QUERY = b'\x1b' + bytes(47)

def ntp_time(host="pool.ntp.org", port=123):
    with socket( AF_INET, SOCK_DGRAM) as s:
        s.sendto(NTP_QUERY, (host, port))
        msg, _ = s.recvfrom(1024)
    return int.from_bytes(msg[-8:], 'big') / 2 ** 32 - NTP_DELTA

if __name__ == "__main__":
    print(time.ctime(ntp_time()))

score 0 · Answer 2 · answered Aug 30 '18 at 17:22

0

The L is not present in python3, that is the first thing you need to change. Convert 2208988800L to 2208988800 read more here

Second, you should rewrite your print command in a print() function. read more here

answered Aug 30 '18 at 17:22

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Python 3.6 conversion of NTP server query function

2 Answers2