I've a script which reads temperature data:
def get_temp(socket, channels):
data = {}
for ch in channels:
socket.sendall('KRDG? %s\n' % ch)
time.sleep(0.2)
temp = socket.recv(32).rstrip('\r\n')
data[ch] = float(temp)
Sometimes, the script fails on the line which converts the values to float:
File "./projector.py", line 129, in get_temp
data[ch] = float(temp)
ValueError: invalid literal for float(): +135.057E+0
+078.260E+0
+00029
but this is NOT an invalid literal. If I enter this into any python shell,
float(+135.057E+0)
then it correctly returns 135.057.
So what is the problem?
Watch out for possible unintended literals in your argument
for example you can have a space within your argument, rendering it to a string / literal:
float(' 0.33')
After making sure the unintended space did not make it into the argument, I was left with:
float(0.33)
Like this it works like a charm.
Take away is: Pay Attention for unintended literals (e.g. spaces that you didn't see) within your input.
I had a similar issue reading the serial output from a digital scale. I was reading [3:12] out of a 18 characters long output string.
In my case sometimes there is a null character "\x00" (NUL) which magically appears in the scale's reply string and is not printed.
I was getting the error:
> ' 0.00'
> 3 0 fast loop, delta = 10.0 weight = 0.0
> ' 0.00'
> 1 800 fast loop, delta = 10.0 weight = 0.0
> ' 0.00'
> 6 0 fast loop, delta = 10.0 weight = 0.0
> ' 0\x00.0'
> Traceback (most recent call last):
> File "measure_weight_speed.py", line 172, in start
> valueScale = float(answer_string)
> ValueError: invalid literal for float(): 0
After some research I wrote few lines of code that work in my case.
replyScale = scale_port.read(18)
answer = replyScale[3:12]
answer_decode = answer.replace("\x00", "")
answer_strip = str(answer_decode.strip())
print(repr(answer_strip))
valueScale = float(answer_strip)
The answers in these posts helped:
Source: Stackoverflow.com