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From "Zoltan Fedor (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (AVRO-1737) Python 3.4 - unhashable type: 'RecordSchema'
Date Fri, 11 Sep 2015 22:38:45 GMT

     [ https://issues.apache.org/jira/browse/AVRO-1737?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zoltan Fedor updated AVRO-1737:
-------------------------------
    Description: 
Following the standard example from http://avro.apache.org/docs/current/gettingstartedpython.html
but adding a dict.get() lookup using an avro.schema.RecordSchema object fails due to "unhashable
type: 'RecordSchema'"

This likely happens because the RecordSchema class overwrites the __eq__ method but does NOT
define a __hash__ method.

Check the Python 3 manual on object.__hash__ (https://docs.python.org/3.1/reference/datamodel.html?highlight=hash#object.%5F%5Fhash%5F%5F):
"If a class does not define an __eq__() method it should not define a __hash__() operation
either; if it defines __eq__() but not __hash__(), its instances will not be usable as items
in hashable collections."


TO REPRODUCE the issue run the following script in Python 3 (tested in Python 3.4.3):
import avro.schema
from avro.datafile import DataFileReader, DataFileWriter
from avro.io import DatumReader, DatumWriter

schema = avro.schema.Parse(open("users.avsc").read())

writer = DataFileWriter(open("users.avro", "wb"), DatumWriter(), schema)
writer.append({"name": "Alyssa", "favorite_number": 256})
writer.append({"name": "Ben", "favorite_number": 7, "favorite_color": "red"})
writer.close()

reader = DataFileReader(open("users.avro", "rb"), DatumReader())
for user in reader:
    print(user)
reader.close()

# added to generate the error
test = {}
test.get(schema, -1)


  was:
Following the standard example from http://avro.apache.org/docs/current/gettingstartedpython.html
but adding a dict.get() lookup using an avro.schema.RecordSchema object fails due to "unhashable
type: 'RecordSchema'"

This likely happens because the RecordSchema class overwrite the __eq__ method but does NOT
define a __hash__ method.

To reproduce run the following script in Python 3 (tested in Python 3.4.3):
import avro.schema
from avro.datafile import DataFileReader, DataFileWriter
from avro.io import DatumReader, DatumWriter

schema = avro.schema.Parse(open("users.avsc").read())

writer = DataFileWriter(open("users.avro", "wb"), DatumWriter(), schema)
writer.append({"name": "Alyssa", "favorite_number": 256})
writer.append({"name": "Ben", "favorite_number": 7, "favorite_color": "red"})
writer.close()

reader = DataFileReader(open("users.avro", "rb"), DatumReader())
for user in reader:
    print(user)
reader.close()

# added to generate the error
test = {}
test.get(schema, -1)



> Python 3.4 - unhashable type: 'RecordSchema'
> --------------------------------------------
>
>                 Key: AVRO-1737
>                 URL: https://issues.apache.org/jira/browse/AVRO-1737
>             Project: Avro
>          Issue Type: Bug
>          Components: python
>    Affects Versions: 1.7.7
>         Environment: Python 3.4, avro 1.7.7
>            Reporter: Zoltan Fedor
>
> Following the standard example from http://avro.apache.org/docs/current/gettingstartedpython.html
but adding a dict.get() lookup using an avro.schema.RecordSchema object fails due to "unhashable
type: 'RecordSchema'"
> This likely happens because the RecordSchema class overwrites the __eq__ method but does
NOT define a __hash__ method.
> Check the Python 3 manual on object.__hash__ (https://docs.python.org/3.1/reference/datamodel.html?highlight=hash#object.%5F%5Fhash%5F%5F):
> "If a class does not define an __eq__() method it should not define a __hash__() operation
either; if it defines __eq__() but not __hash__(), its instances will not be usable as items
in hashable collections."
> TO REPRODUCE the issue run the following script in Python 3 (tested in Python 3.4.3):
> import avro.schema
> from avro.datafile import DataFileReader, DataFileWriter
> from avro.io import DatumReader, DatumWriter
> schema = avro.schema.Parse(open("users.avsc").read())
> writer = DataFileWriter(open("users.avro", "wb"), DatumWriter(), schema)
> writer.append({"name": "Alyssa", "favorite_number": 256})
> writer.append({"name": "Ben", "favorite_number": 7, "favorite_color": "red"})
> writer.close()
> reader = DataFileReader(open("users.avro", "rb"), DatumReader())
> for user in reader:
>     print(user)
> reader.close()
> # added to generate the error
> test = {}
> test.get(schema, -1)



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