Runtimeerror: module compiled against api version 0xb but this version of numpy is 0xa

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You need to compile a module against a compatible API version to prevent the RuntimeError: module compiled against API version 0xb but this version of NumPy is 0xa from occuuring. Hence, to ensure that a numpy module compiles with a suitable API version, we can follow the followig two requirements;

1. Recompile the module.

2. Upgrade the version of Numpy.

While going through the steps to manage the error is an infamous head-scratcher, we dive deep to delve into it and explore the complete steps for resolving the error.

What is the RuntimeError: module compiled against API version 0xb but this version of NumPy is 0xa

As stated earlier, the main reason that results in the error getting prompted is because of the mismatch between the NumPy version that’s getting used and the version of the compiled module. A NumPy API which is not backward compatible implies that a module that was compiled under a high API might fail to execute while using a lower NumPy version, resulting in the error.

NumPy is an important library that is used for scientific computing, providing different functions and methods when working with linear algebra, statistics, arrays, and matrices, among more. To ensure the library is effective and performs seamlessly, the library further undergoes frequent updates.

The version of an API in NumPy is determined by values in the NPY_API_VERSION macro, that’s present in the header file named numpyconfig.h. The version then gets updated and hence increased when a change entailing a change of the types, constants, and changing, removing, or adding, among others, is conducted on its public interface.

The __version__ attribute encodes the API version of NumPy as a hexadecimal number. You will find the NumPy version 1.19.5, implying that the API version is in the form 0x5, whereby the value 5 is a hexadecimal. Further, the module that uses the features of NumPy is encoded in the attribute __version__ through a hexadecimal that’s often presented after the sign +. Here is a sample case; 1.8.0+cu11 that shows that torch compiled with 0xb API version, that’s 11 in hexadecimal.

An example case where you can encounter the error is, for example, you’ve got a compiled module that’s set to interact with NumPy but when you try to import it in your program or script, you find the error. Here’s is the code triggering the error:

import numpy as np
import cv


RuntimeError: module compiled against API version 0xb but this version of NumPy is 0xa

The error message is straightforward in directing the cause; that is being that the module was compiled against version Oxb but the NumPy version getting used at the moment is 0xa. Hence, the mismatch between the Numpy version and the compiled module prompts the runtime error.

Solutions to RuntimeError: module compiled against API version 0xb but this version of NumPy is 0xa

While the error is inconveniencing when you are on programming tasks, you can solve the error by fixing the mismatch that exists between the versions of NumPy in separate ways:

Solution One: Recompiling the module

One of the simplest ways for managing RuntimeError: module compiled against API version 0xb but this version of NumPy is 0xa is through recompiling the module causing the error with the version of NumPy during execution. This way, both the versions of NumPy and the compiled module are compatible.

Hence, reinstalling and updating the module causing the error solves the error since the causes might be older API versions.

Here is a sample case:

# Update to the latest version
pip install torch --upgrade

The command proceeds to install the latest torch version that requires and would have otherwise been compatible with the latest numpy API version.

You can as well specify the version of torch that you would want installed. For example;

# Install torch 1.8.0 with CUDA 11.1 and cuDNN 8.0.5
pip install torch==1.8.0+cu111 torchvision==0.9.0+cu111 torchaudio==0.8.0 -f

That is a command installing torch 1.8.0 with cuDNN 8.0.5 and CUDA 11.1 that has API version of 0xb.

Solution Two: Updating the NumPy version.

Alternatively, you can opt to resolve the error by updating the NumPy library so that it aligns with that of the compiled module. It is more ideal for the version of NumPy to match or exceed that of the API. You can do so by also updating the Python environment or the virtual environment to ensure that there is consistency.

To install specific versions or update to the latest versions, you can update to the latest versions through pip or conda. Here we use pip:

Here is how you can opt to go about it:

# Update numpy to the latest version
pip install numpy –upgrade

The command above installs the latest version of NumPy that has got the highest version of API that’s present.

At times, you may want to use a specific version. Here is the code that specifies the version with the use of the == operator;

# Install numpy 1.19.5
pip install numpy==1.19.5

The above code installs NumPy version 1.19.5 that has the 5 in hexadecimal.

Tip: It is recommended to keep the libraries you are working with updated to prevent similar compatibility issues. Further, check the compatibility table to identify specific numpy versions along with their specific API versions.


Now you are equipped to solve RuntimeError: module compiled against API version 0xb but this version of NumPy is 0xa head-on. Feel free to share your experiences, including any inquiries in the comment section below.


* NumPy Official Documentation:
* GitHub Issue:

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