# Error in generating ligand topology using CGenFF and python 3.9

**URL:** <https://gromacs.bioexcel.eu/t/error-in-generating-ligand-topology-using-cgenff-and-python-3-9/8516>\
**Category:** User discussions\
**Tags:** forcefield, python\
**Created:** [March 5, 2024, 6:59pm UTC](https://gromacs.bioexcel.eu/t/error-in-generating-ligand-topology-using-cgenff-and-python-3-9/8516 "2024-03-05T18:59:44Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Ygya](https://avatars.discourse-cdn.com/v4/letter/y/5f8ce5/32.png) [@Ygya](https://gromacs.bioexcel.eu/u/Ygya)\
**Post date:** [March 5, 2024, 6:59pm UTC](https://gromacs.bioexcel.eu/t/error-in-generating-ligand-topology-using-cgenff-and-python-3-9/8516/1 "2024-03-05T18:59:44Z")

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GROMACS version: 5.1.2  
GROMACS modification: No  
Python version:3.9  
After using this command `python3 cgenff_charmm2gmx_py3_nx2.py JZ4 jz4_fixed.mol2 jz4.str charmm36-jul2022.ff`  
( I used this command to install networkx to solve gcd error: conda install -y networkx"\>=2.5")  
I get the following error:

 ![IMG_20240305_204406_102](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/8/8e23529968802824e88e99bdc4b18fa9580f7724.jpeg)  
What’s wrong and how can i solve it?

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**Author:** ![chenfeng](https://avatars.discourse-cdn.com/v4/letter/c/f04885/32.png) [@chenfeng](https://gromacs.bioexcel.eu/u/chenfeng)\
**Post date:** [March 6, 2024, 7:23am UTC](https://gromacs.bioexcel.eu/t/error-in-generating-ligand-topology-using-cgenff-and-python-3-9/8516/2 "2024-03-06T07:23:31Z")

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maybe you can try to get “network v2.3”,using “pip install” or “conda install”