# How to modify a Dict, which value is array **URL:** \ **Category:** Support: How do I do ...?\ **Created:** [December 30, 2022, 4:09pm UTC](https://numba.discourse.group/t/how-to-modify-a-dict-which-value-is-array/1713 "2022-12-30T16:09:33Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![YiNANzhang](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/yinanzhang/32/745_2.png) [@YiNANzhang](https://numba.discourse.group/u/YiNANzhang)\ **Post date:** [December 30, 2022, 4:09pm UTC](https://numba.discourse.group/t/how-to-modify-a-dict-which-value-is-array/1713/1 "2022-12-30T16:09:33Z")
Want to modify a Dict member variable using a class member function, the value of dict is np.array, but an error occurs, the code is ```auto import numba as nb import numpy as np spec = [ ('x', int32), ('d', nb.types.DictType(nb.types.unicode_type, nb.float64[:])) ] @jitclass(spec) class Cls(): def __init__ (self, x, d): self.x = x self.d = d print('construct') def func(self): d['1'] = np.zeros(3) print('foo') # @njit # def foo(d): # d['1'] = np.zeros([2, 3]) # print('foo') # return d @njit def bar(): # d = Dict() d = Dict.empty(nb.types.unicode_type, nb.float64[:]) # d = foo(d) c = Cls(2,d) c.func() bar() ``` The error message is: ```auto --------------------------------------------------------------------------- TypingError Traceback (most recent call last) Cell In [143], line 32 29 c = Cls(2,d) 30 c.func() ---> 32 bar() 33 # foo(c.func()) File /Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/numba/core/dispatcher.py:468, in _DispatcherBase._compile_for_args(self, *args, **kws) 464 msg = (f"{str(e).rstrip()} \n\nThis error may have been caused " 465 f"by the following argument(s):\n{args_str}\n") 466 e.patch_message(msg) --> 468 error_rewrite(e, 'typing') 469 except errors.UnsupportedError as e: 470 # Something unsupported is present in the user code, add help info 471 error_rewrite(e, 'unsupported_error') File /Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/numba/core/dispatcher.py:409, in _DispatcherBase._compile_for_args..error_rewrite(e, issue_type) 407 raise e 408 else: --> 409 raise e.with_traceback(None) TypingError: Failed in nopython mode pipeline (step: nopython frontend) No implementation of function Function() found for signature: >>> getitem(class(float64), slice) There are 22 candidate implementations: - Of which 22 did not match due to: Overload of function 'getitem': File: : Line N/A. With argument(s): '(class(float64), slice)': No match. During: typing of intrinsic-call at /var/folders/t6/ydb73_8x2slgl6l38dtgksf00000gn/T/ipykernel_69043/638724852.py (27) During: typing of static-get-item at /var/folders/t6/ydb73_8x2slgl6l38dtgksf00000gn/T/ipykernel_69043/638724852.py (27) File "../../../../../var/folders/t6/ydb73_8x2slgl6l38dtgksf00000gn/T/ipykernel_69043/638724852.py", line 27: ``` Does this error occur because Dict does not know Array shape? How should you change the code? ---
**Author:** ![luk-f-a](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/luk-f-a/32/56_2.png) [@luk-f-a](https://numba.discourse.group/u/luk-f-a)\ **Post date:** [December 31, 2022, 7:38am UTC](https://numba.discourse.group/t/how-to-modify-a-dict-which-value-is-array/1713/2 "2022-12-31T07:38:26Z")
hi @YiNANzhang it turned out that the problem was not the dictionary, but the array type definition. The getitem operation on `float64` could not be performed inside an njit function. I fixed it in this example below. Please also note that there was a missing `self.` when calling property `d`. I fixed that too. ```auto import numba as nb import numpy as np from numba.typed import Dict spec = [ ('x', nb.types.int32), ('d', nb.types.DictType(nb.types.unicode_type, nb.float64[:])) ] @jitclass(spec) class Cls(): def __init__ (self, x, d): self.x = x self.d = d print('construct') def func(self): self.d['1'] = np.zeros(3) print('foo') # @njit # def foo(d): # d['1'] = np.zeros([2, 3]) # print('foo') # return d arr_ty = nb.float64[:] @nb.njit def bar(): # d = Dict() d = Dict.empty(nb.types.unicode_type, arr_ty) # d = foo(d) c = Cls(2, d) c.func() bar() ``` ---
**Author:** ![YiNANzhang](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/yinanzhang/32/745_2.png) [@YiNANzhang](https://numba.discourse.group/u/YiNANzhang)\ **Post date:** [December 31, 2022, 10:24am UTC](https://numba.discourse.group/t/how-to-modify-a-dict-which-value-is-array/1713/3 "2022-12-31T10:24:12Z")
Thank you very much for your reply. One question is, why does `arr_ty` have to be a global variable, and why can’t `arr_ty` be resolved when defined in `Dict.empty()` ---
**Author:** ![luk-f-a](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/luk-f-a/32/56_2.png) [@luk-f-a](https://numba.discourse.group/u/luk-f-a)\ **Post date:** [December 31, 2022, 2:38pm UTC](https://numba.discourse.group/t/how-to-modify-a-dict-which-value-is-array/1713/4 "2022-12-31T14:38:00Z")
`arr_ty` is a type instance. `nb.float64[:]` is an operation that creates a type instance. Type instances cannot be created inside `njit` functions. The instance must be created outside. For example, `unicode_type` is also a type instance, which has been created outside the function, as a module-level variable in `nb.types` and imported as a module-level variable into this module. `arr_ty` is the same, it must exist as a variable outside the function and then used. ---
**Author:** ![YiNANzhang](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/yinanzhang/32/745_2.png) [@YiNANzhang](https://numba.discourse.group/u/YiNANzhang)\ **Post date:** [January 3, 2023, 2:03am UTC](https://numba.discourse.group/t/how-to-modify-a-dict-which-value-is-array/1713/5 "2023-01-03T02:03:32Z")
I see. Thanks very much.