# Is there a way to include a Jitclass in another Jitclass?

**URL:** <https://numba.discourse.group/t/is-there-a-way-to-include-a-jitclass-in-another-jitclass/352>\
**Category:** Support: How do I do ...?\
**Created:** [November 18, 2020, 5:28pm UTC](https://numba.discourse.group/t/is-there-a-way-to-include-a-jitclass-in-another-jitclass/352 "2020-11-18T17:28:03Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![stuartarchibald](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/stuartarchibald/32/10_2.png) [@stuartarchibald](https://numba.discourse.group/u/stuartarchibald)\
**Post date:** [November 18, 2020, 5:28pm UTC](https://numba.discourse.group/t/is-there-a-way-to-include-a-jitclass-in-another-jitclass/352/1 "2020-11-18T17:28:03Z")

</div>

This question gets asked relatively often, here’s an example of one way to do it:

```python
import numpy as np
from numba import int64
from numba.experimental import jitclass

spec_foo = {'data': int64[:]}

@jitclass(spec_foo)
class Foo(object):
    def __init__ (self, init_data):
        self.data = init_data

# Want to have a Foo instance in the Bar class
spec_bar = {'foo_inst': Foo.class_type.instance_type}

@jitclass(spec_bar)
class Bar(object):

    def __init__ (self, foo_data):
        # This constructs the Foo instance in the Bar constructor
        self.foo_inst = Foo(foo_data)

# Want to have a Foo instance in the Baz clazz
spec_baz = {'foo_inst': Foo.class_type.instance_type}

@jitclass(spec_baz)
class Baz(object):

    def __init__ (self, foo_inst):
        # This assigns a reference to the Foo instance in the Bar constructor
        self.foo_inst = foo_inst

x = np.arange(5).astype(np.int64)
# Build a Bar instance
bar = Bar(x)
print(bar.foo_inst.data)

# Create a Baz instance that holds a reference to Bar's Foo instance.
baz = Baz(bar.foo_inst)

# Do some arithmetic...
baz.foo_inst.data += 1
print(baz.foo_inst.data)
print(bar.foo_inst.data)

```

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<div class="post-metadata">

**Author:** ![EPronovost](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/epronovost/32/63_2.png) [@EPronovost](https://numba.discourse.group/u/EPronovost)\
**Post date:** [November 22, 2020, 5:23am UTC](https://numba.discourse.group/t/is-there-a-way-to-include-a-jitclass-in-another-jitclass/352/2 "2020-11-22T05:23:26Z")

</div>

As of Numba 0.52 you can also use the new jitclass spec syntax.

```auto
import numpy as np
from numba import int64
from numba.experimental import jitclass

spec_foo = {'data': int64[:]}

@jitclass(spec_foo)
class Foo(object):
    def __init__ (self, init_data):
        self.data = init_data
        
@jitclass
class Bar(object):
    foo_inst: Foo

    def __init__ (self, foo_data):
        # This constructs the Foo instance in the Bar constructor
        self.foo_inst = Foo(foo_data)

@jitclass
class Baz(object):
    foo_inst: Foo

    def __init__ (self, foo_inst):
        # This assigns a reference to the Foo instance in the Bar constructor
        self.foo_inst = foo_inst

x = np.arange(5).astype(np.int64)
# Build a Bar instance
bar = Bar(x)
print(bar.foo_inst.data)

# Create a Baz instance that holds a reference to Bar's Foo instance.
baz = Baz(bar.foo_inst)

# Do some arithmetic...
baz.foo_inst.data += 1
print(baz.foo_inst.data)
print(bar.foo_inst.data)

```

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<div class="post-metadata">

**Author:** ![stuartarchibald](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/stuartarchibald/32/10_2.png) [@stuartarchibald](https://numba.discourse.group/u/stuartarchibald)\
**Post date:** [November 23, 2020, 9:43am UTC](https://numba.discourse.group/t/is-there-a-way-to-include-a-jitclass-in-another-jitclass/352/3 "2020-11-23T09:43:18Z")

</div>

Thanks for sharing @EPronovost 🙂

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<div class="post-metadata">

**Author:** ![alanlujan91](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/alanlujan91/32/83_2.png) [@alanlujan91](https://numba.discourse.group/u/alanlujan91)\
**Post date:** [November 27, 2020, 3:17am UTC](https://numba.discourse.group/t/is-there-a-way-to-include-a-jitclass-in-another-jitclass/352/4 "2020-11-27T03:17:13Z")

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I need a jitclass that has takes as attribute a list of itself jitclasses. I’m trying this

```
@jitclass(spec=[("values", types.List(Bar.class_type.instance_type))])
class JitList(object):
    def __init__ (self, values):
        self.values = values

FooList = JitList([bar])

```

but get the following error:

Failed in nopython mode pipeline (step: nopython mode backend)  
Cannot cast ListType[instance.jitclass.Bar#2c5f1d61490\<foo\_inst:instance.jitclass.Foo#2c5efef29a0\<data:array(int64, 1d, A)\>\>] to list(instance.jitclass.Bar#2c5f1d61490\<foo\_inst:instance.jitclass.Foo#2c5efef29a0\<data:array(int64, 1d, A)\>\>)\<iv=None\>: %".68" = load {i8\*, i8\*}, {i8\*, i8\*}\* %"$8call\_method.3"

Any suggestions?

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<div class="post-metadata">

**Author:** ![stuartarchibald](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/stuartarchibald/32/10_2.png) [@stuartarchibald](https://numba.discourse.group/u/stuartarchibald)\
**Post date:** [November 27, 2020, 1:42pm UTC](https://numba.discourse.group/t/is-there-a-way-to-include-a-jitclass-in-another-jitclass/352/5 "2020-11-27T13:42:25Z")

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Hi @alanlujan91

I suggest writing a copy-pasteable reproducer so that someone can take a look at the code in more detail by running it locally. Perhaps even start a new topic with the reproducer?

Many thanks.