How to find the line that is generating a Pandas SettingWithCopyWarning?

Question

I have a large block of code that is, at some point somewhere, generating a setting with copy warning in pandas (this problem).

I know how to fix the problem, but I

Answer 1

Set pd.options.mode.chained_assignment = 'raise'

This will throw an exception pointing to the line which triggers SettingWithCopyError.

UPDATE: how to catch the error, and interrogate the stacktrace to get the actual offending lineno:

import pandas as pd
from inspect import currentframe, getframeinfo
from pandas.core.common import SettingWithCopyError

pd.options.mode.chained_assignment = 'raise'

df = pd.DataFrame({'a': [1, 2, 3], 'b': [4, 5, 6]})

df2 = df[df['a'] == 2]

try:
    df2['b'] = 'foo'
except SettingWithCopyError:
    print('handling..')
    frameinfo = getframeinfo(currentframe())
    print(frameinfo.lineno)