如何使此功能在Python上更有效？

Question

I am working on a script for an automated workflow. It expects a CSV and a disk image to be present in the directory that is supplied as args.input.

I want to check for and handle every possible scenario: no CSV, no disk image, too many CSVs, too many disk images, and any possible combination thereto.

I've written the below, which works, and seems to be human readable, but it just seems incredibly excessive and verbose – is there any way I can make this more compact, yet still retain its legibility?

# CONFORMANCE CHECKS
def check_conformance():
    csv = glob.glob(args.input+'*.csv')
    disk_image = glob.glob(args.input+'*.E01')

    if len(csv) == 1:
        does_csv_exist = os.path.isfile(csv[0])
    elif len(csv) < 1:
        does_csv_exist = False
    elif len(csv) > 1:
        does_csv_exist = "too many CSVs!"
    if len(disk_image) == 1:
        does_E01_exist = os.path.isfile(disk_image[0])
    elif len(disk_image) < 1:
        does_E01_exist = False
    elif len(disk_image) > 1:
        does_E01_exist = "too many Disk Images!"
    if len(disk_image) > 1 and len(csv) > 1:
        does_csv_exist = "too many CSVs!"
        does_E01_exist = "too many disk images!"
        return (False, does_csv_exist, does_E01_exist,)
    if does_E01_exist is True and does_csv_exist is True:
        return True
    elif does_E01_exist is True and does_csv_exist is False:
        return (False, "CSV is missing")
    elif does_E01_exist is False and does_csv_exist is True:
        return (False, "E01 disk image is missing")
    elif does_E01_exist is False and does_csv_exist is False:
        return (False, "E01 disk image AND csv are missing")
    elif does_csv_exist is not True and does_csv_exist is not False:
        return (False, does_csv_exist)
    elif does_E01_exist is not True and does_E01_exist is not False:
        return (False, does_E01_exist)

Answer 1

I'm not sure exactly what the purpose of this function is, but here are a few tips:

• A function should have just one function. Yours seems to have multiple - return whether or not the input conforms to your standards ( True/False ) and return some sort of error string ( str ). You are returning tuples that combine these two things in unpredictable ways. Either pick one or the other, or standardize the tuple and always return the same exact one (ie (bool, str) )

• Even though you can set multiple different types to the same variable, you shouldn't. Don't set a Boolean in one condition, and then a string in another condition (see: does_csv_exist )

I would have done something like this:

# CONFORMANCE CHECKS
# Returns a list of error strings encountered, empty list if OK
def getConformanceErrors():
    csv = glob.glob(args.input+'*.csv')
    disk_image = glob.glob(args.input+'*.E01')

    msg = []

    if len(csv) < 1:
        msg.append("CSV is missing")
    elif len(csv) > 1:
        msg.append("Too many CSVs")  

    if len(disk_image) < 1:
        msg.append("Disk Image is missing")
    elif len(disk_image) > 1:
        msg.append("Too many Disk Images") 

    return msg