splitting time (h,m,s) from dataframe column

[volcano63]

Check_Out_Minutes = mydata['Check Out'].apply(time_to_minutes)

Output:
And it returns an attribute error 

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-13-d84e37515c72> in <module>()
----> 1 Check_Out_Minutes = mydata['Check Out'].apply(time_to_minutes)

C:\Program Files\Anaconda3\lib\site-packages\pandas\core\series.py in apply(self, func, convert_dtype, args, **kwds)
   2549             else:
   2550                 values = self.asobject
-> 2551                 mapped = lib.map_infer(values, f, convert=convert_dtype)
   2552 
   2553         if len(mapped) and isinstance(mapped[0], Series):

pandas/_libs/src/inference.pyx in pandas._libs.lib.map_infer()

<ipython-input-5-c033186c9b10> in time_to_minutes(time_str)
      1 def time_to_minutes(time_str):
      2     try:
----> 3         hours, minutes, seconds = time_str.split(':')
      4     except ValueError:
      5         return

AttributeError: 'datetime.time' object has no attribute 'split'

As the exception message states, mydata['Check Out'] Series contain objects of type datetime.time - and you try to treat them as strings.

Change your function to calculate time from datetime.time object - and you are set

Output:
In [22]: def time_2_mins(t):
    ...:     return t.hour * 60 + t.minute + t.second / 60
    ...: times = pd.Series([time(12, 15, 40), time(8, 25, 6)])
    ...: print(times)
    ...: times.apply(time_2_mins)
    ...: 
    ...: 
0    12:15:40
1    08:25:06
dtype: object
Out[22]: 
0    735.666667
1    505.100000
dtype: float64