CODEWITHSUNDEEP
pythoncontinuetry-except
Coldchain9
Coldchain9

Reputation: 1745

How to skip one part of a single loop iteration in Python

I am creating about 200 variables within a single iteration of a python loop (extracting fields from excel documents and pushing them to a SQL database) and I am trying to figure something out.

Let's say that a single iteration is a single Excel workbook that I am looping through in a directory. I am extracting around 200 fields from each workbook.

If one of these fields I extract (lets say field #56 out of 200) and it isn't in proper format (lets say the date was filled out wrong ie. 9/31/2015 which isnt a real date) and it errors out with the operation I am performing.

I want the loop to skip that variable and proceed to creating variable #57. I don't want the loop to completely go to the next iteration or workbook, I just want it to ignore that error on that variable and continue with the rest of the variables for that single loop iteration.

How would I go about doing something like this?

In this sample code I would like to continue extracting "PolicyState" even if ExpirationDate has an error.

Some sample code:

import datetime as dt
import os as os
import xlrd as rd

files = os.listdir(path)

for file in files: #Loop through all files in path directory  
            filename = os.fsdecode(file) 
            if filename.startswith('~'): 
                continue

            elif filename.endswith( ('.xlsx', '.xlsm') ): 
                try:
                    book = rd.open_workbook(os.path.join(path,file)) 
                except KeyError:
                    print ("Error opening file for "+ file) 
                    continue

                    SoldModelInfo=book.sheet_by_name("SoldModelInfo")
                    AccountName=str(SoldModelInfo.cell(1,5).value)
                    ExpirationDate=dt.datetime.strftime(xldate_to_datetime(SoldModelInfo.cell(1,7).value),'%Y-%m-%d')
                    PolicyState=str(SoldModelInfo.cell(1,6).value)
                    print("Insert data of " + file +" was successful")
            else:
               continue

Upvotes: 0

Views: 1236

Answers (3)

alberand
alberand

Reputation: 662

So, basically you need to wrap your xldate_to_datetime() call into try ... except

import datetime as dt

v = SoldModelInfo.cell(1,7).value

try:
    d = dt.datetime.strftime(xldate_to_datetime(v), '%Y-%m-%d')
except TypeError as e:
    print('Could not parse "{}": {}'.format(v, e)

Upvotes: 1

r.ook
r.ook

Reputation: 13898

As suggested you could use multiple try blocks on each of your extract variable, or you could streamline it with your own custom function that handles the try for you:

from functools import reduce, partial

def try_funcs(cell, default, funcs):
    try:
        return reduce(lambda val, func: func(val), funcs, cell)
    except Exception as e:
        # do something with your Exception if necessary, like logging.
        return default

# Usage:

AccountName = try_funcs(SoldModelInfo.cell(1,5).value, "some default str value", str)
ExpirationDate = try_funcs(SoldModelInfo.cell(1,7).value), "some default date", [xldate_to_datetime, partial(dt.datetime.strftime, '%Y-%m-%d')])
PolicyState = try_funcs(SoldModelInfo.cell(1,6).value, "some default str value", str)

Here we use reduce to repeat multiple functions, and pass partial as a frozen function with arguments.

This can help your code look tidy without cluttering up with lots of try blocks. But the better, more explicit way is just handle the fields you anticipate might error out individually.

Upvotes: 1

nigel222
nigel222

Reputation: 8222

Use multiple try blocks. Wrap each decode operation that might go wrong in its own try block to catch the exception, do something, and carry on with the next one.

            try:
                book = rd.open_workbook(os.path.join(path,file)) 
            except KeyError:
                print ("Error opening file for "+ file) 
                continue

            errors = []

            SoldModelInfo=book.sheet_by_name("SoldModelInfo")
            AccountName=str(SoldModelInfo.cell(1,5).value)
            try:
                ExpirationDate=dt.datetime.strftime(xldate_to_datetime(SoldModelInfo.cell(1,7).value),'%Y-%m-%d')
            except WhateverError as e:
                # do something, maybe set a default date?
                ExpirationDate = default_date
                # and/or record that it went wrong?
                errors.append( [ "ExpirationDate", e ])
            PolicyState=str(SoldModelInfo.cell(1,6).value)
            ...
            # at the end
            if not errors:
                print("Insert data of " + file +" was successful")
            else:
                # things went wrong somewhere above. 
                # the contents of errors will let you work out what

Upvotes: 2

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