Replacing column values in pandas with specific column with multiple database operation?
You can use the python ternary operator with list comprehension:

df['Buckets(HRS)'] =
 ['&lt;2hrs' if x&lt;=120 else '2-4' if 120&gt;x&lt;=240 else '4-6' if 240&gt;x&lt;=360 else '&gt;6' for x in db['Stoppage time in minutes']]