Checking module name inside 'except ImportError'

user_548894 0
Viewed 7657
try:
   import MySQLdb
   # some action
except ImportError as err:
   # fallback code

PyCharm gives a code inspection warning on that:

'MySQLdb' in try block with 'except ImportError' should also be defined in except block

This inspection detects names that should resolve but don't. Due to dynamic dispatch and duck typing, this is possible in a limited but useful number of cases. Top-level and class-level items are supported better than instance items.

Ok, I thought the warning is reasonable, because the fallback code assumes that 'MySQLdb' is not installed, while it could be some different error that just raised ImportError. So I used something like:

try:
   import MySQLdb
   # some action
except ImportError as err:
   if "MySQLdb" in repr(err):
       # fallback code
   else:
       raise

The PyCharm alert is still exists, but It could be just a PyCharm issue (google shows issues with such inspections)

Questions:

  1. Is it really worth checking for name when you "except ImportError"? Even in simple cases (no some action after import MySQLdb)?

  2. If it worth checking, Is the above example the right way to do it? If no - what is the right way?

P.S. MySQLdb is just an example of a module that could be absent in the system.

pycharm importerror exception-handling python
4 Answers

One method of getting the name, already mentioned is using the name attribute:

try:
    import pty
except ImportError as e:
    print(e.name)

However, it is important to note that you might not get the module name you started with; namely, running the above on Windows gives you termios as the output, not pty.

To maintain compatibility with python 2.7 (for those who haven't made the switch, you're on the clock)

try:
    import pty
except ImportError as e:
    print(e.args[0].rsplit(' ',1)[-1])  # `msg` attribute is `message` on python2...stick with args

# prints the same result: termios

Some bonus tidbits:

  • Python 3.6 was released around the end of 2016. Since it's 2019+, you can opt for the clearer exception ModuleNotFoundError:

    A subclass of ImportError which is raised by import when a module could not be located. It is also raised when None is found in sys.modules.

  • If you are using Python 3.3+, don't forget about the path attribute (in addition to the name already mentioned), which gives the path to any file that raised the exception (only useful in more complex cases -- in simple examples like the one I gave path will return None.)

user_73141800

Try this:

try:
  import libname
except ImportError as e:
       e = e[0][16:]
       print("\n[!] Error: Please Install Module Name:[ {} ] And Try Again !!!".format(e))
       exit(1)

Output:

[!] Error: Please Install Module Name:[ libname ] And Try Again !!!

user_106567240
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