Python 值错误

Question

尝试将管道输出拆分为 python 时出现错误。

错误是 need more than 3 values to unpack 虽然我使用了 8 个值

import subprocess, sys

from datetime import datetime

from time import sleep as sleep



multimon_ng = subprocess.Popen("multimon-ng -a FLEX -t wav flex.wav",
    stdout=subprocess.PIPE,
    stderr=subprocess.PIPE,
    shell=True)

while True:
        nextline = multimon_ng.stdout.readline()
        flex, mdate, mtime, bitrate, other, capcode, o2, msg  = nextline.split(" ", 7)      # error here
        if nextline is " ":
            print "napping"
        else:
            print mdate + " " + mtime + " " + capcode + " " + msg

        multimon_ng.poll()
        sys.stdout.flush()

任何帮助都会很棒

Answer 1

错误消息中的

3 指示右侧参数中可迭代的长度。

最少的错误示例：

a, = []  # ValueError: need more than 0 values to unpack
a, b = [1]  # ValueError: need more than 1 value to unpack
a, b, c = [1, 2]  # ValueError: need more than 2 values to unpack
# etc ...

最少的正确示例：

a, = [1]
a, b = [1, 2]
a, b, c = [1, 2, 3]

修复和暴露问题的最小变化是将解包迭代包装在 try-except 块中。

while True:
    nextline = multimon_ng.stdout.readline()

    if not nextline:
        print "napping"
    else:
        try:
            flex, mdate, mtime, bitrate, other, capcode, o2, msg  = nextline.split(" ", 7)
        except ValueError:
            print "invalid line", nextline
        else:
            print mdate + " " + mtime + " " + capcode + " " + msg

    multimon_ng.poll()
    sys.stdout.flush()

如您所见，我还移动了解包前的空行检查。如果行为空，解包也会失败。

Python 值错误

Python Value error

subprocess

stdout

python-2.7

raspberry-pi

flex-paging