lookslike 0.9

Compare dictionaries, lists and other objects convenient and readable

Lookslike - Simple datatype comparison

Lookslike is a library to simplify comparison of two objects (like numbers) within complex structures (like dictionaries) in a simple and readable way.

For example it can be used to compare JSON data from server responses.

A simple example would be this:

{'num': 42, 'alph': 'abcd'} == {'num': Like(int), 'alph': Like(str)} # -> True

Usage

import re
from lookslike import Like, utils

# This basically meant to simplify object comparison:
server_response = {'timestamp': 42, 'uuid': 'abcd'} 
server_response == {'timestamp': Like(int), 'uuid': Like(str)}  # True

# Check for type
42 == Like(int)  # True
42 == Like(float)  # False

# Check using regular expressions
'abc' == Like(re.compile("a.*"))  # True
'abc' == Like(re.compile('a'))  # False
123.456 == Like(re.compile("\d+\.\d+"))  # True

# Check using custom function
42 == Like(lambda value: 40 < value < 44)  # True

# Combine multiple checks
42 == Like(int, lambda value: 40 < value < 44)  # True
42 == Like(float, lambda value: 40 < value < 44)  # False

# Convert values
['c', 'b', 'a'] == Like(['a', 'b', 'c'], convert=sorted)  # True
{'a': 1, 'b': 'not important'} == Like({'a': 1},
                                       convert=utils.filter_keys(['a']))  # True


# "Real world" example
def test_server_response():
    server_response = {  # This is your test object of course
        'response_id': 42,
        'timestamp': 2134567.2355,
        'pets': ['cat', 'dog', 'chicken'],
        'number_of_pets': 3,
        'info_url': 'https://petsdb.info/',
        'vet name': 'Dr. Murphey',
        'home': {
            'home_id': 1242,
            'address': {
                'street': 'Rabbit street 42',
                'city': 'New Bark',
            }
        }
    }

    assert server_response == {
        'response_id': Like(int),
        'timestamp': Like(float),
        'pets': Like(['cat', 'chicken', 'dog'], convert=sorted),
        'number_of_pets': 3,
        'info_url': Like(lambda value: value.startswith('https://')),
        'vet name': Like(re.compile('Dr\. .*')),
        'home': {
            'home_id': Like(int),
            'address': Like({'city': 'New Bark'}, convert=utils.filter_keys(['city']))
        }
    }  # True

To consider

When you provide a regex pattern, there are some things to consider:

Pattern has to match the whole string

When you provide a regex Pattern, it has to match the whole string. This is to prevent False-positives. For example:

This regex re.match("a", "abc") will find a match. But "abc" == Like(re.compile("a")) will be False. Instead you have to use "abc" == Like(re.compile("a.*")

Comparing strings with bytes does not raise an Exception

Normally, you will get a TypeError when doing something like this re.match(b'abc', 'a') However, this b'abc' == Like(re.compile("a") will return False instead without raising an exception.

Other utilities

If you want to compare JSON only and want a tool that is more standardized you can have a look at jsonschema.

If you want not only to check, but to convert dictionaries to real Python objects, have a look at pydantic.