In Python, how does one catch warnings as if they were exceptions?

In Python, how does one catch warnings as if they were exceptions?

To handle warnings as errors simply use this:

import warnings
warnings.filterwarnings(error)

After this you will be able to catch warnings same as errors, e.g. this will work:

try:
    some_heavy_calculations()
except RuntimeWarning:
    import ipdb; ipdb.set_trace()

P.S. Added this answer because the best answer in comments contains misspelling: filterwarnigns instead of filterwarnings.

To quote from the python handbook (27.6.4. Testing Warnings):

import warnings

def fxn():
    warnings.warn(deprecated, DeprecationWarning)

with warnings.catch_warnings(record=True) as w:
    # Cause all warnings to always be triggered.
    warnings.simplefilter(always)
    # Trigger a warning.
    fxn()
    # Verify some things
    assert len(w) == 1
    assert issubclass(w[-1].category, DeprecationWarning)
    assert deprecated in str(w[-1].message)

In Python, how does one catch warnings as if they were exceptions?

If you just want your script to fail on warnings you can invoke python with the -W argument:

python -W error foobar.py

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