python - 名称错误 : name 'altitude' is not defined

Question

我有这个 gps 代码，它获取 gps 数据并写入日志:

#!/usr/bin/python

from systemd import journal
import gps
import time
import threading
import datetime

# Listen on port 2947 (gpsd) of localhost
session = gps.gps("localhost", "2947")
session.stream(gps.WATCH_ENABLE | gps.WATCH_NEWSTYLE)

while True:
    try:
        report = session.next() # Wait for a 'TPV' report and display 
the current time

        # To see all report data, uncomment the line below
        #print report

        if report['class'] == 'TPV':
            if hasattr(report, 'time'):
                timestamp = (time.time()*1000)
                #print timestamp

            if hasattr(report, 'lat'):
                latitude = report.lat
                #print latitude

            if hasattr(report, 'lon'):
                longitude = report.lon
                #print longitude    

            if hasattr(report, 'alt'):
                altitude = report.alt
                #print altitude

        else:
            timestamp = (time.time()*1000)
            latitude = 0
            longitude = 0 
            altitude = 0

        journal.send(
        channel = 'gps',
        priority = journal.Priority.INFO,
        timestamp = "%f" % (timestamp),
        latitude = "%f" % (latitude),
        longitude = "%f" % (longitude), 
        altitude = "%f" % (altitude), 
        )

except KeyError:
    pass
except KeyboardInterrupt:
    quit()
except StopIteration:
    session = None
    print "GPSD has terminated"

我得到这个错误:

Traceback (most recent call last):
  File "gps-messi.py", line 57, in <module>
    altitude = "%f" % (altitude),
NameError: name 'altitude' is not defined

有趣的是代码有时工作得很好，有时却给我这个错误。我不明白我应该怎么做才能让它一直正常工作。这和她的爆炸有什么关系吗？

Answer 1

我的猜测是 if hasattr(report, 'alt'): 没有解析为 True，那么

if hasattr(report, 'alt'):
    altitude = report.alt

不会为 altitude 分配任何东西，当你到达这里时就在那里

journal.send(
    channel = 'gps',
    priority = journal.Priority.INFO,
    timestamp = "%f" % (timestamp),
    latitude = "%f" % (latitude),
    longitude = "%f" % (longitude), 
    altitude = "%f" % (altitude), 
    )

在分配之前，您实际上是在使用 altitude。为避免这种情况，您可以在到达此点之前将 altitude 初始化为某个值

altitude=0

这样做将确保它在使用之前就已分配，并且您不应该得到该错误。