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.

W.X · Accepted Answer · 2022-08-23 11:28:18Z

2

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！

edited Aug 23, 2022 at 11:28

answered Aug 18, 2022 at 4:33

W.X

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1 Comment

Chris Over a year ago

Welcome to Stack Oveflow. Code is a lot more helpful when it is accompanied by an explanation. Stack Overflow is about learning, not providing snippets to blindly copy and paste. Please edit your answer and explain how it answers the specific question being asked. See How to Answer.

0xc0de · Accepted Answer · 2021-03-31 09:24:28Z

0

It is returning data with byte type, to get it in str type, you have to call .decode method on it. Here is the documentation for that: https://docs.python.org/3/library/stdtypes.html#bytes.decode

answered Mar 31, 2021 at 9:24

0xc0de

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