Shouldn't the try: import in init re-raise original exception? · Issue #23868 · pandas-dev/pandas (original) (raw)

Problem description

It is confusing when import pandas raises a message like:

>>> import pandas
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/raf/anaconda3/lib/python3.7/site-packages/pandas/__init__.py", line 19, in <module>
    "Missing required dependencies {0}".format(missing_dependencies))
ImportError: Missing required dependencies ['pytz']

Where actually the true error is not in pytz, but in a missing library required by pytz:

>>> import pytz
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/raf/anaconda3/lib/python3.7/site-packages/pytz/__init__.py", line 20, in <module>
    from pytz.tzinfo import unpickler, BaseTzInfo
  File "/home/raf/anaconda3/lib/python3.7/site-packages/pytz/tzinfo.py", line 4, in <module>
    from bisect import bisect_right
ImportError: cannot import name 'bisect_right' from 'bisect' (/home/raf/tmp/bisect.py)

As you can see, I happen to have a file called bisect.py in the same folder where I'm trying to import pandas, but the error message raised by pandas doesn't reflect that. It was a silly error after all, but It gave me a headache to sort that out.

Tracking back the source of it, in pandas/__init__.py, note that the original error e is not used after except ImportError as e. I think it should.

for dependency in hard_dependencies:
    try:
        __import__(dependency)
    except ImportError as e:
        missing_dependencies.append(dependency)

if missing_dependencies:
    raise ImportError(
        "Missing required dependencies {0}".format(missing_dependencies))

Expected Output

raise ImportError(...) should mention the error e raised by __import__(dependency)

Question also asked in SO:
https://stackoverflow.com/questions/53445555/shouldnt-the-try-import-in-init-re-raise-original-exception