AWS Lambda calling DynamoDB put_item gives syntax error

Question

I've created my first Lambda with Python to create a new entry in a DynamoDB table called Users, which has Partition key UserId of type String. I'm calling it using a POST method in my API Gateway using the test function to send a request body of:

{
    "email":"testemail",
    "name":"testname testerson",
    "password":"testpassword1"
}

The idea behind the method is to generate a UUID to use for the primary key, and on the occurrence of it already being in use, generate it again until it is unique. The lambda function is:

def create_user(event, context):
    status_code = 0
    response = ''
    body = event['body']
    
    # check all required fields are present
    if all(key in body.keys() for key in ['email', 'password', 'name']):
        # generate salt and hashed password
        salt = bcrypt.gensalt()
        hashed = bcrypt.hashpw(body['password'], salt)
        
        # get users table from dynamodb
        dynamodb = boto3.resource('dynamodb')
        table = dynamodb.Table('Users')
        
        inserted = False
        while not inserted:
            user_id = uuid.uuid4().hex
            try:
                response = table.put_item(
                    Item={
                        'UserId' = user_id,
                        'name' = body['name'],
                        'email' = body['email'],
                        'password' = hashed,
                        'salt' = salt
                    },
                    ConditionExpression = 'attribute_not_exists(UserId)'
                )
            except Exception as e:
                if e.response['Error']['Code'] == "ConditionalCheckFailedException":
                    continue
                status_code = 500
                response = 'Could not process your request'
                break
            else:
                status_code = 200
                response = 'Account successfully created'
                inserted = True
    else:
        status_code = 400
        response = 'Malformed request'
    
    return {
        'statusCode': status_code,
        'body': json.dumps(response)
    }

The syntax error appears in the logs on the line containing 'UserId' = user_id,, but I have no idea why.

Any help would be appreciated!

Please repeat on topic and How to Ask from the tour. "Teach me this basic language feature" is off-topic for Stack Overflow. Stack Overflow is not intended to replace existing tutorials and documentation. — TigerhawkT3
– TigerhawkT3, Commented Mar 1, 2021 at 4:04
For future reference, if you get a Syntax Error, the first thing would be check the appropriate syntax for what you are doing. — Abrar Hossain
– Abrar Hossain, Commented Mar 1, 2021 at 4:16

rdas · Accepted Answer · 2021-03-01 04:03:45Z

3

There are 2 standard ways of defining dictionary literals

Item={
    'UserId' = user_id,
    'name' = body['name'],
    'email' = body['email'],
    'password' = hashed,
    'salt' = salt
}

This is not one of them.

You can either do:

Item={
    'UserId': user_id,
    'name': body['name'],
    'email': body['email'],
    'password': hashed,
    'salt': salt
}

Or:

Item=dict(
    UserId=user_id,
    name=body['name'],
    email=body['email'],
    password=hashed,
    salt=salt
}

answered Mar 1, 2021 at 4:03

rdas

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1 Comment

Paragon_ Over a year ago

Can’t believe I missed this, thanks for pointing it out!

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