Getting JSON serializable error for datetime

Question

I am trying to fetch the CloudFormation stack details using boto3 as below

import boto3
import json

def lambda_handler(event, context):
    global cnfOutput
    cnfOutput = cfn1.describe_stacks(StackName='cfn-init-stack1')
    cnf2 = json.dumps(cnfOutput)
    return cnf2

Below is the output I get if I print cfnOutput. I tried to do json.dumps and getting the error. Please need help

{u'Stacks': [{u'StackId': 'arn:aws:cloudformation:us-west-2:123456789123:stack/cfn-init-stack1/d209-11e8-b83e-0ad6ed005066', u'Description': 'CloudFormation template for creating an ec2 instance', u'Parameters': [{u'ParameterValue': 'e1', u'ParameterKey': 'KeyName'}, {u'ParameterValue': 'ami-a0cfeed8', u'ParameterKey': 'ImageId'}, {u'ParameterValue': 't2.micro', u'ParameterKey': 'InstanceType'}], u'Tags': [], u'Outputs': [{u'Description': 'The public name of the EC2 instance.', u'OutputKey': 'PublicName', u'OutputValue': 'ec2-51-111-211-211.us-west-2.compute.amazonaws.com'}], u'RoleARN': 'arn:aws:iam::123456789123:role/CFN1-role', u'EnableTerminationProtection': False, u'CreationTime': datetime.datetime(2018, 10, 17, 12, 40, 10, 783000, tzinfo=tzlocal()), u'StackName': 'cfn-init-stack1', u'NotificationARNs': ['arn:aws:sns:us-west-2:123456789123:topic2'], u'StackStatus': 'CREATE_COMPLETE', u'DisableRollback': False, u'RollbackConfiguration': {u'RollbackTriggers': []}}], 'ResponseMetadata': {'RetryAttempts': 0, 'HTTPStatusCode': 200, 'RequestId': 'd20e-11e8-b15b-a11f0bf7ba', 'HTTPHeaders': {'x-amzn-requestid': 'd20e-11e8-b15b-a11f0bf7ba', 'date': 'Wed, 17 Oct 2018 13:13:11 GMT', 'content-length': '2010', 'content-type': 'text/xml'}}}

Getting below error

File "/usr/lib64/python2.7/json/encoder.py", line 184, in default raise TypeError(repr(o) + " is not JSON serializable") TypeError: datetime.datetime(2018, 10, 17, 12, 40, 10, 783000, tzinfo=tzlocal()) is not JSON serializable

Bilal Saleem · Accepted Answer · 2018-10-17 16:50:42Z

2

How to convert the original dictionary to JSON

The following ran for me without issues:

j = json.dumps({"key": str(datetime.datetime(2017, 10, 12, 12, 40, 10, 783000))})

However, when I ran it as:

j = json.dumps({"key": datetime.datetime(2017, 10, 12, 12, 40, 10, 783000)})

I got the same error as you.

If you can convert the result of datetime.datetime(2018, 10, 17, 12, 40, 10, 783000, tzinfo=tzlocal()) to a string before calling json.dumps, it should fix your issue.

How to extract OutputValue from original dictionary

# d is your original dictionary
# after you convert the datetime.datetime() result to string
d = {
    u'Stacks': [{
        u'StackId': 'arn:aws:cloudformation:us-west-2:123456789123:stack/cfn-init-stack1/d209-11e8-b83e-0ad6ed005066', 
        u'Description': 'CloudFormation template for creating an ec2 instance', u'Parameters': [{
            u'ParameterValue': 'e1', u'ParameterKey': 'KeyName'
        }, {
            u'ParameterValue': 'ami-a0cfeed8', u'ParameterKey': 'ImageId'
        }, {
            u'ParameterValue': 't2.micro', u'ParameterKey': 'InstanceType'
        }], u'Tags': [], u'Outputs': [{
            u'Description': 'The public name of the EC2 instance.', u'OutputKey': 'PublicName', u'OutputValue': 'ec2-51-111-211-211.us-west-2.compute.amazonaws.com'
        }], u'RoleARN': 'arn:aws:iam::123456789123:role/CFN1-role', u'EnableTerminationProtection': False, u'CreationTime': str(datetime.datetime(2018, 10, 17, 12, 40, 10, 783000)), u'StackName': 'cfn-init-stack1', u'NotificationARNs': ['arn:aws:sns:us-west-2:123456789123:topic2'], u'StackStatus': 'CREATE_COMPLETE', u'DisableRollback': False, u'RollbackConfiguration': {
            u'RollbackTriggers': []
        }
    }], 
    'ResponseMetadata': {
        'RetryAttempts': 0,
        'HTTPStatusCode': 200,
        'RequestId': 'd20e-11e8-b15b-a11f0bf7ba',
        'HTTPHeaders': {
            'x-amzn-requestid': 'd20e-11e8-b15b-a11f0bf7ba',
            'date': 'Wed, 17 Oct 2018 13:13:11 GMT',
            'content-length': '2010',
            'content-type': 'text/xml'
        }
    }
}

stacks = d.get("Stacks")

if stacks == None:
    print("Key not in dictionary")
else:
    for s in stacks:
        outputs = s.get("Outputs")
        if outputs == None:
            continue

        for o in outputs:
            print(o.get("OutputValue"))

Output for me is ec2-51-111-211-211.us-west-2.compute.amazonaws.com when using the dictionary in your question (after converting datetime.datetime() result to a string but before converting the whole dictionary to JSON).

edited Oct 17, 2018 at 16:50

answered Oct 17, 2018 at 14:48

Bilal Saleem

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4 Comments

RaghuCK Over a year ago

I want to extract the "OutputValue" from the above after converting the output to json. So please tell me how to do it.

Bilal Saleem Over a year ago

When you convert your dictionary to JSON then it will a string object and therefore it will be better if you extracted the value first and then converted it to JSON.

Bilal Saleem Over a year ago

I'm not sure if the above is what you were looking for but have a look. In your cfn1.describe_stacks method, try to return the results of datetime.datetime() within your dictionary as a string. If you can do that then the above is how you can extract "OutputValue"

Polv Over a year ago

I would convert using datetime.strftime(DATETIME_FORMAT). This will allow deconverting use datetime.strptime(DATETIME_FORMAT). docs.python.org/3/library/…

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