time data "STR" does not match format '%H:%M:%S'-CodePudding

I'm trying to import and visualize data from an Excel sheet using Pandas and Matplotlib.

The data file is in ISO 8601 with 4 Hz. What I want to do is show the x-axis with only HH:MM:SS and a lower tick rate, 30-60 seconds.

I managed to convert from ISO 8601 to HH:MM:SS with the following:

data["Time UTC"] = [element[10:19] for element in data["Time_4Hz"]]

Then I want to define the left and right range as follows:

for element in data.index:
    x_limit_l = min(datetime.strptime(element, '%H:%M:%S'))
    x_limit_r = max(datetime.strptime(element, '%H:%M:%S'))

and get the following error:

ValueError: time data ' 08:45:27' does not match format '%H:%M:%S'

The time should be a string with the correct format, what could be the reason for the error?

I tried looping through the "Time UTC" colum with:

for element in data.index:
    x_limit_l = min(datetime.strptime(element, '%H:%M:%S'))
    x_limit_r = max(datetime.strptime(element, '%H:%M:%S'))

I also tried getting the time directly from the column with:

    x_limit_l = min(datetime.strptime("data.index", '%H:%M:%S'))
    x_limit_r = max(datetime.strptime("data.index", '%H:%M:%S'))

CodePudding user response：

Looks like there are spaces in the str which raises the Exception. To fix that, you can use strip function. If you don't know about it, it just removes spaces from start and end of str.

x_limit_l = datetime.strptime(element.strip(), '%H:%M:%S')

EDIT: For the error you are getting after implementing, there's no use of using min in a single value excluding the fact that datetime object cannot be iterable.

Here's a working work-around, assuming you can apply logic yourself:

x_limit_list = list() #Creates a list

for element in data.index:
    #Just showing of one element
    x_limit_l = x_limit_list.append(datetime.strptime(element, '%H:%M:%S'))
    #Adds the current x_limit_l value to the list

#After the loop ends, it finds the min value
x_limit_l = min(x_limit_list)

#If you want it in Hour, Min and Sec format:
x_limit_l = min(x_limit_list).strftime('%H:%M:%S')

CodePudding user response：

Should it not be data["Time UTC"] = [element[11:19] for element in data["Time_4Hz"]]?

import pandas as pd
from datetime import datetime
lst = ['2022-12-06 12:42:40Z','2022-12-06 12:44:40Z','2022-12-06 12:46:40Z','2022-12-06 12:48:40Z']
data = pd.DataFrame(lst, columns =['Time_4Hz'])
data["Time UTC"] = [element[11:19] for element in data["Time_4Hz"]]
x_limit_l = print(max(data["Time UTC"]))
x_limit_r = print(min(data["Time UTC"]))
print(x_limit_l, x_limit_r)

No need to loop