Python:无法解决全局变量错误

Question

即使在我将变量声明为全局变量之后，我也会收到此错误，因为未定义全局名称。我不确定我是否已在正确的位置将变量声明为全局变量。

我在这个程序中尝试做的是从函数 lux（） 我将原始数据从传感器读取到 var 中。传感器原始数据有两个值，光度和红外。我将它们分别分配给通道 0 和通道 1。在函数 getLux（） 中，我使用 channel0 和 channel1 来计算增益值。

请帮我解决此错误

#!/usr/bin/python
import time
import smbus
from smbus import SMBus
address = 0x39
control = 0x03
tsl = SMBus(1)
pause = 0.08
def lux():
    #global channel0
    #global channel1
    print "Workking"
    tsl.write_byte(address, 0x80)
    tsl.write_byte(address, control)
    var = [0, 0, 0, 0]
    var = tsl.read_i2c_block_data(0x39, 0x8d)
    channel0 = ((var[1]<<8) + var[0])
    channel1 = ((var[3]<<8) + var[2])
    print "total light %5d     IR light %5d" % (channel0, channel1)
    time.sleep(2)
    return (channel0, channel1)
def setGain(gain):
    if (gain == 1):
            tsl.write_byte_data(address, 0x81, 0x01)
    elif (gain == 16):
            tsl.write_byte_data(address, 0x81, 0x11)
    time.sleep(pause)
def getLux(gain):
    global channel0
    global channel1
    if (gain == 1 or gain == 16):
            setGain(gain)
            ambient = lux(channel0)
            IR = lux(channel1)
    elif (gain == 0):
            setGain(16) #first try high gain
            ambient = channel0
            if (ambient < 65535):
                    IR = channel1
            if (ambient >= 65535):
                    setGain(1) #set low gain
                    ambient = channel0
                    IR = channel1
    if (gain == 1):
            ambient *= 16 #scale 1x to 16x
            IR *= 16
   if (float(ambient == 0)):
            ratio = 9999
    else:
            ratio = (IR / float(ambient))
    if (ratio >= 0) & (ratio <= 0.52):
            tlux = (0.0315 * ambient) - (0.0593 * ambient * (ratio**1.4))
    elif (ratio <= 0.65):
            tlux = (0.299 * ambient) - (0.0291 * IR)
    elif (ratio <= 0.80):
            tlux = (0.0157 * ambient) - (0.018 * IR)
    elif (ratio <= 1.3):
            tlux = (0.00338 * ambient) - (0.0026 * IR)
    elif (ratio > 1.3):
            tlux = 0
    return tlux

while True:
    print "LUX High Gain ", getLux(16)
    print "LUX Low Gain ", getLux(1)
    print "LUX AUTO Gain ", getLux()

Traceback (most recent call last): File "lux2.py", line 85, in <module> print "LUX High Gain ", getLux(16) File "lux2.py", line 45, in getLux ambient = lux(channel0) NameError: global name 'channel0' is not defined

Answer 1

您可以将 channel0 和 channel1 作为 getLux 函数的属性：

getLux(gain, channel0, channel1)

然后执行代码可能如下所示：

while True:
    channels = lux() # This creates a tuple with channel variables
    print "LUX High Gain ", getLux(16, channels[0], channels[1])
    print "LUX Low Gain ", getLux(1, channels[0], channels[1])
    print "LUX AUTO Gain ", getLux(0, channels[0], channels[1])

这样，您就不需要将它们声明为全局的，这通常被认为是不安全的做法。

Answer 2

我看到的问题是你还没有初始化全局变量。 您需要初始化getLux函数中的全局变量，例如。

global channel0
global channel1
channel0 = 0
channel1 = 0

这将解决问题。

你可以全局声明 channel0、channel1，以便在任何函数中访问、分配和重新分配，而不是使用 global 关键字。