Python：针对X轴上的时间绘制数据

Question

I got data like this and i wanna plot temperature vs time

time=`['16:00:00', '16:00:00.013733', '16:00:00.020599', '16:00:00.034332', 
'16:00:00.041199', '16:00:00.048065', '16:00:00.061798', '16:00:00.068665', 
'16:00:00.075531', '16:00:00.089264', '16:00:00.102997', '16:00:00.109863', 
'16:00:00.123596', '16:00:00.130463', '16:00:00.137329', '16:00:00.151062', 
'16:00:00.157928', '16:00:00.171661', '16:00:00.178528', '16:00:00.192261']`

temperature=`[ 691.70001221,  691.54998779,  691.90002441,  691.79998779,
               691.29998779,  691.65002441,  691.59997559,  691.79998779,
               691.95001221,  692.34997559,  691.59997559,  691.34997559,
               690.90002441,  691.40002441,  691.95001221,  690.84997559,
               691.54998779,  691.70001221,  691.95001221,  691.59997559]`

i tried to this

import datetime as DT
datetimes = [DT.datetime.strptime(t, "%H:%M:%S") for t in time]

and i stop here because it appears an error

ValueError: unconverted data remains: .013733

i think referred to decimals of seconds in the time arrange

Thanks

Answer 1

Your times are formatted in two different ways (ie one without fractions of seconds, the others with), so you will need to try the two formats:

datetimes = []
for t in time:
    try:
        datetimes.append(DT.datetime.strptime(t, "%H:%M:%S"))
    except ValueError:
        datetimes.append(DT.datetime.strptime(t, "%H:%M:%S.%f"))

Alternatively, if you are sure that none of the rest will have no fractions of seconds, you could treat the first separately:

datetimes = ([DT.datetime.strptime(time[0], "%H:%M:%S")] + 
             [DT.datetime.strptime(t, "%H:%M:%S.%f") for t in time[1:]])

Answer 2

You have a heterogeneous collection of format strings. Some (the first) is in the format "%H:%M:%S" , and some (the rest) is in the format "%H:%M:%S.%f" . So write a helper function:

def datetime_helper(formats, s):
    for f in formats:
        try:
            return datetime.strptime(s, f)
        except ValueError:
            pass

then you can do:

my_formats = "%H:%M:%S.%f","%H:%M:%S"

[datetime_helper(my_formats,x) for x in time]