如何忽略非浮点值

Question

我有一个USB温度记录器,每隔30秒上传到Cosm.我遇到的问题是,每运行5分钟,当我运行命令时,它会报告文本错误而不是数字.

所以我试图找到一种方法来让它循环,直到它收到一个数字或只是忽略文本并恢复脚本(否则退出,否则).

我非常不优雅的解决方案是这样做:

  # convert regular error message to number
    if temp_C == "temporarily": # "temporarily" is used as it happens to be the 4th word in the error message
            temp_C = 0.0

目前的代码是:

while True:
    # read data from temper usb sensor
    sensor_reading=commands.getoutput('pcsensor')

    #extract single temperature reading from the sensor

    data=sensor_reading.split(' ') #Split the string and define temperature
    temp_only=str(data[4]) #knocks out celcius reading from line
    temp=temp_only.rstrip('C') #Removes the character "C" from the string to allow for plotting

    # calibrate temperature reading
    temp_C = temp

    # convert regular error message to number
    if temp_C == "temporarily":
            temp_C = 0.0

    # convert value to float
    temp_C = float(temp_C)

    # check to see if non-float
    check = isinstance(temp_C, float)

    #write out 0.0 as a null value if non-float
    if check == True:
            temp_C = temp_C
    else:
            temp_C = 0.0

Answer 1

在Python中,要求宽恕通常比允许(EAFP)更容易.遇到a时ValueError,continue到下一次迭代:

try:
    temp_C = float(temp_C)
except ValueError:
    continue # skips to next iteration

或者更紧凑(巩固你的大部分功能):

try:
    temp_C = float(sensor_reading.split(' ')[4].rstrip('C'))
except (ValueError, IndexError):
    continue