Readme examples do not cover update and filter

[baynes]

The examples in the READMEdo not cover the update and filter functions. There is no documentation on these leading to puzzles as how to use them - see #42 - and many readers may not even realize the functionality is even there. I propose the following is added:

# Modifying values matching path
>>> jsonpath_expr.update( {'foo': [{'baz': 1}, {'baz': 2}]}, 3)
{'foo': [{'baz': 3}, {'baz': 3}]}

# Modifying one of the values matching path
>>> matches = jsonpath_expr.find({'foo': [{'baz': 1}, {'baz': 2}]})
>>> matches[0].full_path.update( {'foo': [{'baz': 1}, {'baz': 2}]}, 3)
{'foo': [{'baz': 3}, {'baz': 2}]}

# Removing all values matching path
>>> jsonpath_expr.filter(lambda d: True, {'foo': [{'baz': 1}, {'baz': 2}]})
{'foo': [{}, {}]}

# Removing values containing particular data matching path
>>> jsonpath_expr.filter(lambda d: d == 2, {'foo': [{'baz': 1}, {'baz': 2}]})
{'foo': [{'baz': 1}, {}]}

[WilliamYuhangLee]

The filter() function does not work when there is a filter expression in the jsonpath, and it throws a NotImplementedError. Code to duplicate this error:

obj = {
    "a": [
        {"b": "X"},
        {"b": "Y"}
    ]
}

jsonpath = parse("$.a[?(@.b==X)]")

matches = jsonpath.find(obj)
print(matches[0].value)
>>> {'b': 'X'}  # find() returns correct value

result = jsonpath.filter(lambda x: True, obj)
>>> NotImplementedError  # filter() throws error

[baynes]

The filter() function does not work when there is a filter expression in the jsonpath, and it throws a NotImplementedError. Code to duplicate this error:

obj = {
    "a": [
        {"b": "X"},
        {"b": "Y"}
    ]
}

jsonpath = parse("$.a[?(@.b==X)]")

matches = jsonpath.find(obj)
print(matches[0].value)
>>> {'b': 'X'}  # find() returns correct value

result = jsonpath.filter(lambda x: True, obj)
>>> NotImplementedError  # filter() throws error

@WilliamYuhangLee: I think what you have found is an interaction between the use of filter member function and the filter extensions to JSONPath. I don't think it affects my proposed documentation additions above. I suggest you raise what you have found as a separate issue.

[michaelmior]

@baynes I added these examples. Thanks!