How is deserialization affected by only and partial?

Nobody has claimed this yet.

I was hoping to get some clarification on the differences between `only` and `partial` with respect to deserialization. (This question is similar to #509 which addresses serialization using the same fields.) Based on the docs and the response to that issue, I interpreted it to mean that `only` applies to serialization and `partial` applies to deserialization. However, in testing it looks like `only` also affects deserialization. What am I missing?

``` python
from marshmallow import Schema, fields

class MySchema(Schema):
foo = fields.Field(required=True)
bar = fields.Field(required=True)

only_schema = MySchema(only=('foo', ))
partial_schema = MySchema(partial=True)

print(only_schema.load({'foo': 42, 'bar': 24}))
print(only_schema.load({'foo': 42}))
print(partial_schema.load({'foo': 42, 'bar': 24}))
print(partial_schema.load({'foo': 42}))
```

Output:

``` python
UnmarshalResult(data={u'foo': 42}, errors={})
UnmarshalResult(data={u'foo': 42}, errors={})
UnmarshalResult(data={'foo': 42, 'bar': 24}, errors={})
UnmarshalResult(data={'foo': 42}, errors={})
```

I expected deserialization using `only_schema` to result in an error similar to the example below.

``` python
MySchema().load({'foo':42})
```

Output:

``` python
UnmarshalResult(data={'foo': 42}, errors={'bar': [u'Missing data for required field.']})
```

Ultimately, I'm trying to get away with using the same schema for (de)serialization, but maybe that's not the ideal way to use marshmallow.

Read the documentation for `only` and `partial`, then compare their deserialization behavior with the serialization discussion in issue #509. Done means the intended distinction is established and the documentation or issue guidance clearly explains whether one schema should support both operations.

Written by the indexing model from the issue text.