Concatenate String in Python

Question

I am looking to create a string of all errors returned from the API. There may be multiple errors returned in a list. Each error is a dict and the string I wish to access its the reason:

  result: {
       errors: [{
          error: 'invalid_input',
          code: 409,
          reason: 'the inputted date field does not match required format'

       },
       {
          error: 'invalid_input',
          code: 409,
          reason: 'the inputted message field does not match required format'
        }

  }

What I have tried is:

return_string = ""
if errors in result:
    for error in errors:
        returned_string += " {}".format(error['reason'])

Is there a more pythonic way to do it?

returned_string += " {}".format(error['reason')

Rakesh
– Rakesh

2018-02-13 13:18:01 +00:00
Commented Feb 13, 2018 at 13:18 — Rakesh
– Rakesh, Commented Feb 13, 2018 at 13:18
return_string* ?

Ankush Rathi
– Ankush Rathi

2018-02-13 13:19:01 +00:00
Commented Feb 13, 2018 at 13:19 — Ankush Rathi
– Ankush Rathi, Commented Feb 13, 2018 at 13:19

Thomas · Accepted Answer · 2018-02-13 16:57:18Z

4

There are several typos in your code. But the more Pythonic way would be with a ~~list comprehension~~ generator expression:

return_string = ""
if "errors" in result:
    return_string = " ".join(error['reason'] for error in result['errors'])

Or even in one line:

return_string = " ".join(error['reason'] for error in result.get('errors', []))

edited Feb 13, 2018 at 16:57

answered Feb 13, 2018 at 13:20

Thomas

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1 Comment

Chris_Rands Over a year ago

you mean a generator expression, no list comprehensions here

Rakesh · Accepted Answer · 2018-02-13 13:20:49Z

0

result = {
       "errors": [{
          "error": 'invalid_input',
          "code": 409,
          "reason": 'the inputted date field does not match required format'

       },
       {
          "error": 'invalid_input',
          "code": 409,
          "reason": 'the inputted message field does not match required format'
        }]

  }

return_string = ""
if result.get("errors", None):
    for error in result["errors"]:
        return_string += " {}\n".format(error['reason'])
print return_string

Output:

the inputted date field does not match required format
 the inputted message field does not match required format

answered Feb 13, 2018 at 13:20

Rakesh

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Comments

Sohaib Farooqi · Accepted Answer · 2018-02-13 13:56:09Z

You can use operator.itemgetter along with map to fetch the reason key from your list of dicts like

>>> from operator import itemgetter
>>> error_list = list(map(itemgetter('reason'),r['errors']))

This will give you output like

>>> ['the inputted date field does not match required format', 'the inputted message field does not match required format']

Next you can use join to join these strings together as one error message

>>> "".join(error_list)
>>> 'the inputted date field does not match required formatthe inputted message field does not match required format'

You can also specify the character on which you want seperate these two string

>>> " ".join(error_list) #Whitespace
>>> 'the inputted date field does not match required format the inputted message field does not match required format'

If you prefer one-liners

>>> " ".join(map(itemgetter('reason'),r['errors']))

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