Code that produced the error

Oct 13, 2025 by talynt.org 18 views

What happened?

Polymarket's matchOrders function, as seen on PolygonScan, is supposed to have a selector of 0xd2539b37. However, the function_abi_to_4byte_selector() function returns 0xe60f0c05.

Although the issue was initially suspected to be with the web3py library, further investigation revealed that the root cause lies within the eth-utils library.

Code that produced the error

pol_contract_addr = "0x4bFb41d5B3570DeFd03C39a9A4D8dE6Bd8B8982E"
pol_abi_addr = f"https://api.polygonscan.com/api?module=contract&action=getabi&address={pol_contract_addr}&apikey={pol_api_key}"
pol_abi_data = requests.get(pol_abi_addr).json()
contract_instance = w3.eth.contract(address=pol_contract_addr, abi=pol_abi_data['result'])

from web3.utils import get_abi_element_info

# debug step into this function
get_abi_element_info(contract_instance.abi, "matchOrders")

Full error output

just the wrong output, but as a consequence of that: 

Web3ValueError: Could not find any function with matching selector

Possible solutions

After further investigation, it appears that the issue lies within the eth-utils library. The function_abi_to_4byte_selector() function is not correctly identifying the selector for the matchOrders function.

To resolve this issue, you can try the following:

Update the eth-utils library to the latest version.
Use a different library to generate the 4-byte selector, such as web3.utils.sha3().

eth-utils Version

The current version of eth-utils is 5.2.0.

Python Version

The current version of Python is 3.11.11.

Operating System

The operating system is Linux (Google Colab).

Output from `pip freeze`

absl-py==1.4.0
accelerate==1.3.0
access==1.1.9
affine==2.4.0
aiohappyeyeballs==2.6.1
aiohttp==3.11.13
aiosignal==1.3.2
alabaster==1.0.0
albucore==0.0.23
albumentations==2.0.5
ale-py==0.10.2
altair==5.5.0
annotated-types==0.7.0
anyio==3.7.1
argon2-cffi==23.1.0
argon2-cffi-bindings==21.2.0
array_record==0.6.0
arviz==0.20.0
astropy==7.0.1
astropy-iers-data==0.2025.3.3.0.34.45
asttokens==3.0.0
astunparse==1.6.3
atpublic==4.1.0
attrs==25.1.0
audioread==3.0.1
autograd==1.7.0
babel==2.17.0
backcall==0.2.0
beautifulsoup4==4.13.3
betterproto==2.0.0b6
bigframes==1.38.0
bigquery-magics==0.6.0
bitarray==3.1.1
bleach==6.2.0
blinker==1.9.0
blis==0.7.11
blosc2==3.2.0
bokeh==3.6.3
Bottleneck==1.4.2
bqplot==0.12.44
branca==0.8.1
CacheControl==0.14.2
cachetools==5.5.2
catalogue==2.0.10
certifi==2025.1.31
cffi==1.17.1
chardet==5.2.0
charset-normalizer==3.4.1
chex==0.1.89
ckzg==2.0.1
clarabel==0.10.0
click==8.1.8
click-plugins==1.1.1
cligj==0.7.2
cloudpathlib==0.21.0
cloudpickle==3.1.1
cmake==3.31.6
cmdstanpy==1.2.5
colorcet==3.1.0
colorlover==0.3.0
colour==0.1.5
comm==0.2.2
community==1.0.0b1
confection==0.1.5
cons==0.4.6
contourpy==1.3.1
cramjam==2.9.1
cryptography==43.0.3
cuda-python==12.6.2.post1
cudf-cu12 @ https://pypi.nvidia.com/cudf-cu12/cudf_cu12-25.2.1-cp311-cp311-manylinux_2_24_x86_64.manylinux_2_28_x86_64.whl
cudf-polars-cu12==25.2.2
cufflinks==0.17.3
cuml-cu12==25.2.1
cupy-cuda12x==13.3.0
cuvs-cu12==25.2.1
cvxopt==1.3.2
cvxpy==1.6.2
cycler==0.12.1
cyipopt==1.5.0
cymem==2.0.11
Cython==3.0.12
cytoolz==1.0.1
dask==2024.12.1
dask-cuda==25.2.0
dask-cudf-cu12==25.2.2
dask-expr==1.1.21
datascience==0.17.6
db-dtypes==1.4.2
dbus-python==1.2.18
debugpy==1.8.13
decorator==5.2.1
defusedxml==0.7.1
Deprecated==1.2.18
deprecation==2.1.0
diffusers==0.32.2
dill==0.3.9
distributed==2024.12.1
distributed-ucxx-cu12==0.42.0
distro==1.9.0
dlib==19.24.2
dm-tree==0.1.9
docker-pycreds==0.4.0
docstring_parser==0.16
docutils==0.21.2
dopamine_rl==4.1.2
duckdb==1.1.3
earthengine-api==1.5.5
easydict==1.13
editdistance==0.8.1
eerepr==0.1.1
einops==0.8.1
en-core-web-sm @ https://github.com/explosion/spacy-models/releases/download/en_core_web_sm-3.7.1/en_core_web_sm-3.7.1-py3-none-any.whl#sha256=86cc141f63942d4b2c5fcee06630fd6f904788d2f0ab005cce45aadb8fb73889
entrypoints==0.4
esda==2.7.0
et_xmlfile==2.0.0
eth-account==0.13.5
eth-hash==0.7.1
eth-keyfile==0.8.1
eth-keys==0.6.1
eth-rlp==2.2.0
eth-typing==5.2.0
eth-utils==5.2.0
eth_abi==5.2.0
etils==1.12.1
etuples==0.3.9
executing==2.2.0
Farama-Notifications==0.0.4
fastai==2.7.18
fastcore==1.7.29
fastdownload==0.0.7
fastjsonschema==2.21.1
fastprogress==1.0.3
fastrlock==0.8.3
filelock==3.17.0
fiona==1.10.1
firebase-admin==6.6.0
Flask==3.1.0
flatbuffers==25.2.10
flax==0.10.4
folium==0.19.5
fonttools==4.56.0
frozendict==2.4.6
frozenlist==1.5.0
fsspec==2024.10.0
future==1.0.0
gast==0.6.0<br/>
# function_abi_to_4byte_selector() returns incorrect selector: A Q&A Article

## Q: What is the `function_abi_to_4byte_selector()` function?

A: The `function_abi_to_4byte_selector()` function is a part of the `eth-utils` library, which is used to generate a 4-byte selector from a function's ABI.

## Q: What is a 4-byte selector?

A: A 4-byte selector is a unique identifier for a function in a smart contract. It is a 4-byte hash of the function's name and signature.

## Q: Why is the `function_abi_to_4byte_selector()` function returning an incorrect selector?

A: The `function_abi_to_4byte_selector()` function is not correctly identifying the selector for the `matchOrders` function. This is likely due to a bug in the function or an issue with the ABI.

## Q: How can I fix the issue with the `function_abi_to_4byte_selector()` function?

A: There are a few possible solutions to this issue:

1.  Update the `eth-utils` library to the latest version.
2.  Use a different library to generate the 4-byte selector, such as `web3.utils.sha3()`.
3.  Check the ABI for the `matchOrders` function to ensure that it is correct.

## Q: What is the current version of the `eth-utils` library?

A: The current version of the `eth-utils` library is 5.2.0.

## Q: What is the current version of Python?

A: The current version of Python is 3.11.11.

## Q: What is the operating system being used?

A: The operating system being used is Linux (Google Colab).

## Q: What is the output from `pip freeze`?

A: The output from `pip freeze` is a list of all the installed packages and their versions.

## Q: How can I update the `eth-utils` library to the latest version?

A: To update the `eth-utils` library to the latest version, you can use the following command:

```bash
pip install --upgrade eth-utils

Q: How can I use a different library to generate the 4-byte selector?

A: To use a different library to generate the 4-byte selector, you can use the following code:

import web3

selector = web3.utils.sha3("matchOrders")

Q: How can I check the ABI for the `matchOrders` function?

A: To check the ABI for the matchOrders function, you can use the following code:

import json

abi = json.loads("your_abi_here")

Replace "your_abi_here" with the actual ABI for the matchOrders function.

Q: What are some common issues that can cause the `function_abi_to_4byte_selector()` function to return an incorrect selector?

A: Some common issues that can cause the function_abi_to_4byte_selector() function to return an incorrect selector include:

A bug in the function or the ABI.
An issue with the ABI, such as a missing or incorrect function signature.
A problem with the eth-utils library, such as an outdated version.

Q: How can I troubleshoot issues with the `function_abi_to_4byte_selector()` function?

A: To troubleshoot issues with the function_abi_to_4byte_selector() function, you can try the following:

Check the ABI for the matchOrders function to ensure that it is correct.
Update the eth-utils library to the latest version.
Use a different library to generate the 4-byte selector, such as web3.utils.sha3().
Check the output from pip freeze to ensure that all packages are up to date.
Try using a different version of Python or a different operating system.