计算员工工作时长报错：TypeError: datetime.time类型不支持减法操作

Hey there, let's sort out that error you're running into! The root issue is that Python's datetime.time objects don't support direct subtraction with the - operator—this arithmetic only works for datetime.datetime types. Below are two practical solutions to calculate your employees' shift working hours correctly:

Solution 1: Convert time columns to datetime objects #

The easiest fix is to convert your Check in and Check out columns from datetime.time to datetime.datetime types, then compute the difference. Here's how to do it in pandas:

import pandas as pd

# Convert time columns to datetime (pandas will auto-add a default date, e.g., 1900-01-01)
data['Check in'] = pd.to_datetime(data['Check in'], format='%H:%M:%S')
data['Check out'] = pd.to_datetime(data['Check out'], format='%H:%M:%S')

# Calculate working duration
data['Thời gian làm việc'] = data['Check out'] - data['Check in']

The result will be a timedelta object, which displays nicely as HH:MM:SS and can be further processed (e.g., extract total hours with .dt.total_seconds() / 3600 if you need numerical values).

If you want to explicitly use the current date instead of pandas' default, you can combine the time values with today's date:

from datetime import date

data['Check in datetime'] = pd.to_datetime(str(date.today()) + ' ' + data['Check in'].astype(str))
data['Check out datetime'] = pd.to_datetime(str(date.today()) + ' ' + data['Check out'].astype(str))
data['Thời gian làm việc'] = data['Check out datetime'] - data['Check in datetime']

Solution 2: Calculate time difference manually (no type conversion) #

If you prefer not to convert the column types, you can calculate the time difference by converting each time to total seconds, subtracting, then formatting back to HH:MM:SS:

def compute_time_diff(check_in, check_out):
    # Convert time to total seconds since midnight
    in_sec = check_in.hour * 3600 + check_in.minute * 60 + check_in.second
    out_sec = check_out.hour * 3600 + check_out.minute * 60 + check_out.second
    diff_sec = out_sec - in_sec
    
    # Convert back to HH:MM:SS format
    hours = diff_sec // 3600
    minutes = (diff_sec % 3600) // 60
    seconds = diff_sec % 60
    return f"{hours}:{minutes:02d}:{seconds:02d}"

# Apply the function to each row
data['Thời gian làm việc'] = data.apply(lambda row: compute_time_diff(row['Check in'], row['Check out']), axis=1)

This gives you a string-formatted time difference. Just note that this won't handle overnight shifts (e.g., check-in at 22:00, check-out at 06:00 next day) automatically—you'd need to add logic to check if check_out is earlier than check_in and adjust the seconds accordingly.

内容的提问来源于stack exchange，提问作者Phuc Coi