Unable to parse AWS DynamoDB binary get item in boto3 python

Question

I have got the items from AWS dynamodb as dict which has a value in binary format. I am not able to retrieve the value of a binary content.

Below is the sample.

my_details  = {'route': Binary(b'gAAAABgLNW9tNcpeclIy1LSs8wKYRy9uMxgr5V4TwJmEJNZ2WVlb3Z3LtIK3PewO2SDRYkvXAh8bcZ4Ej_jBjaNi8xhU1-P2FLpcGEX2g='), 'way': '5064', '
stop': Binary(b'\xf1J\xef\xa0\xac\xb1A0\xa9\\:'), 'name': 'cfcf57'}

print(type(my_details['route']))

print(my_details['route'])
print(my_details['way'])

I need value of the route key like below

gAAAABgLNW9tNcpeclIy1LSs8wKYRy9uMxgr5V4TwJmEJNZ2WVlb3Z3LtIK3PewO2SDRYkvXAh8bcZ4Ej_jBjaNi8xhU1-P2FLpcGEX2g=

I have tried to get the value of route using mydetails['route'] but got below error

<class 'boto3.dynamodb.types.Binary'>
Traceback (most recent call last):
  File "C:/Users/Prabhakar/Documents/Projects/Test.py", line 18, in <module>
    print(my_details['route'])
    
TypeError: __str__ returned non-string (type bytes)

Please let me know how can I retrieve the binary content in python dict.

Answer 1

when you call print(my_details['route']), the actual call is print(str(my_details['route'])).

boto3.dynamodb.types.Binary define is

class Binary:
    """A class for representing Binary in dynamodb

    Especially for Python 2, use this class to explicitly specify
    binary data for item in DynamoDB. It is essentially a wrapper around
    binary. Unicode and Python 3 string types are not allowed.
    """

    def __init__(self, value):
        if not isinstance(value, BINARY_TYPES):
            types = ', '.join([str(t) for t in BINARY_TYPES])
            raise TypeError(f'Value must be of the following types: {types}')
        self.value = value

    def __eq__(self, other):
        if isinstance(other, Binary):
            return self.value == other.value
        return self.value == other

    def __ne__(self, other):
        return not self.__eq__(other)

    def __repr__(self):
        return f'Binary({self.value!r})'

    def __str__(self):
        return self.value

    def __bytes__(self):
        return self.value

    def __hash__(self):
        return hash(self.value)

then the actual call is print(my_details['route'].__str__()), the return type is bytes, so you get the type error:

TypeError: __str__ returned non-string (type bytes)

so what you need is just print(bytes(my_details['route'])), or print(str(bytes(my_details['route'])))

Python's types are really confusing！