Uploaded July 2026 | Updated September 2026, 2 weeks ago
Yujian Tang started coding at 13 — not because someone told him to, but because he thought it was cool. That curiosity took him from NumPy and SciPy in college, to Amazon, to Zilliz (the team behind Milvus, one of the first open source vector databases), to working on some of the earliest LangChain and LlamaIndex builds — before most people knew what an LLM was.
Now he's CEO of OSS4AI and a collaborator with PyData chapters across the US.
"Open source gives you a very low cost of entry. It's basically free to use these tools — and it helps you learn a lot about the technology."
Give Me 5 Season 2, Episode 8 drops tomorrow. 👀
Yujian Tang started coding at 13 — not because someone told him to, but because he thought it was cool. That curiosity took him from NumPy and SciPy in college, to Amazon, to Zilliz (the team behind Milvus, one of the first open source vector databases), to working on some of the earliest LangChain and LlamaIndex builds — before most people knew what an LLM was.
Now he's CEO of OSS4AI and a collaborator with PyData chapters across the US.
"Open source gives you a very low cost of entry. It's basically free to use these tools — and it helps you learn a lot about the technology."
Give Me 5 Season 2, Episode 8 drops tomorrow. 👀
![Solving Marketplace Cold Start at Scale with Ranking [PyCon DE & PyData 2026]](https://i.ytimg.com/vi/xS5xM2ojrH0/mqdefault.jpg "Solving Marketplace Cold Start at Scale with Ranking [PyCon DE & PyData 2026]
🔊 Recorded at PyCon DE & PyData 2026, 14.04.2026
https://2026.pycon.de/talks/GVHZW9/
🎓 Watch Theodore Meynard share a pragmatic blueprint for solving the marketplace cold start problem through scalable ranking strategies and experiment-driven iteration.
Speakers:
Theodore Meynard
Description:
Marketplace cold start occurs when new activities lack the historical data—clicks, bookings, and reviews—required by ranking models to achieve visibility, creating a self-reinforcing loop of low exposure. To break this trap and activate the growth flywheel for new supply, a system was developed to transition from rigid, manual constraints to flexible, ML-driven exploration.
Initial attempts focused on prioritizing a queue of new activities using supplier-level features or filtering out low-scoring candidates, both of which yielded marginal results. A breakthrough occurred when the system replaced random selection with the existing ranking model to pick the best candidates for reserved exposure slots. This increased conversion rates and the total number of activated activities. Subsequent iterations removed the queue and prioritization models entirely, allowing all new and unactivated activities to compete in real-time.
The final architecture replaced fixed exposure slots with a blended score, combining the standard ranking score with a boost factor for unactivated items. This flexible boosting approach increased bookings per visitor for unactivated activities. Key findings indicate that removing hand-crafted constraints increases ML optimization and that framing cold start as a supplier activation problem rather than a customer ranking problem provides clearer business metrics for success.
⭐️ About PyCon DE:
PyCon DE is the leading conference on open-source Python applications in AI and data science. It brings together industry professionals, researchers, AI and data science practitioners, and software engineering communities, providing a unique platform for collaboration, knowledge sharing, and innovation.
The PyCon DE & PyData 2026 conference delivered an exceptional experience, fostering stronger connections within the Python community while showcasing the latest advancements in artificial intelligence and data science. Attendees enjoyed a diverse and engaging program of talks, workshops, and networking opportunities, further establishing the conference as a premier event for Python, AI, and data science enthusiasts across Germany.
PyCon DE 2027 will take place in Heidelberg from 19 to 23 April 2027.
Follow us:
• Newsletter: https://2027.pycon.de/newsletter/
• LinkedIn: https://www.linkedin.com/company/pyconde
• X: https://www.x.com/pyconde
Links:
• Conference website: http://pycon.de
• Other sessions: https://2026.pycon.de/talks/
The conference was organized by
• Python Softwareverband e.V.: http://pysv.org
• Pioneers Hub gemeinnützige GmbH: http://pioneershub.org
in collaboration with NumFOCUS Inc.: http://numfocus.org
If you enjoyed this session, please like, and subscribe to our channel for more insightful talks and discussions.
Share this video with your network to spread the knowledge!
Hashtags:
#Python #PyConDE #PyData #OpenSource #AI #DataScience #MachineLearning #SoftwareEngineering #LLMs #Community #Sovereignty
Acknowledgements:
Special thanks to all the volunteers and sponsors who made this event possible.
About:
Python Softwareverband e.V.:
PySV is a non-profit that promotes the use and development of Python in Germany through events, education, and advocacy, fostering an open Python community.
Pioneers Hub gemeinnützige GmbH:
is a non-profit fostering innovation in AI and tech by connecting experts and promoting knowledge exchange through events and collaborative initiatives.
NumFOCUS Inc.
supports open-source scientific computing by providing financial and logistical support to key projects like NumPy and Jupyter, promoting sustainable development and collaboration.
www.pydata.org
PyData is an educational program of NumFOCUS, a 501(c)3 non-profit organization in the United States. PyData provides a forum for the international community of users and developers of data analysis tools to share ideas and learn from each other. The global PyData network promotes discussion of best practices, new approaches, and emerging technologies for data management, processing, analytics, and visualization. PyData communities approach data science using many languages, including (but not limited to) Python, Julia, and R.")
![Simulating the World using SimPy: A practical Example [PyCon DE & PyData 2026]](https://i.ytimg.com/vi/zayHuvKVr34/mqdefault.jpg "Simulating the World using SimPy: A practical Example [PyCon DE & PyData 2026]
🔊 Recorded at PyCon DE & PyData 2026, 16.04.2026
https://2026.pycon.de/talks/WDHTQR/
🎓 Watch Cloud Engineer Niklas demonstrate how to use SimPy to build reproducible, event-based simulations for testing complex systems and optimizing load-balancing algorithms.
Speakers:
Niklas
Description:
Explainable AI (XAI) addresses the black box problem in machine learning, where models may rely on spurious correlations—such as identifying a wolf based on snow in the background rather than the animals features—to make predictions. To mitigate this, a structured framework distinguishes between interpretability (direct reading of model logic) and explainability (approximations of model behavior). The framework further categorizes analysis by model access (white box vs. black box), scope (global vs. local), and data type (tabular, image, and text).
For tabular data, global explainability focuses on feature ranking, effects, and interactions. SHAP (Shapley Additive Explanations) uses game theory to rank feature importance and visualize how specific values push predictions higher or lower via beeswarm plots. Feature effects are analyzed using Partial Dependence Plots (PDP) for average effects or Accumulated Local Effects (ALE) plots to handle correlated features. Local explainability identifies why a specific prediction occurred using SHAP waterfall plots or LIME (Local Interpretable Model-agnostic Explanations), which fits a local meta-model to the input. Counterfactual analysis, implemented via the DiCE package, functions as a GPS navigator to determine the minimum input changes required to achieve a different target outcome.
For image data, global analysis employs Testing with Concept Activation Vectors (TCAV) to determine if human-defined concepts, such as stripes, influence predictions using directional derivatives. Additionally, feature visualization reveals what a model learns at different layers, progressing from simple patterns to complex structures and specific objects.
⭐️ About PyCon DE:
PyCon DE is the leading conference on open-source Python applications in AI and data science. It brings together industry professionals, researchers, AI and data science practitioners, and software engineering communities, providing a unique platform for collaboration, knowledge sharing, and innovation.
The PyCon DE & PyData 2026 conference delivered an exceptional experience, fostering stronger connections within the Python community while showcasing the latest advancements in artificial intelligence and data science. Attendees enjoyed a diverse and engaging program of talks, workshops, and networking opportunities, further establishing the conference as a premier event for Python, AI, and data science enthusiasts across Germany.
PyCon DE 2027 will take place in Heidelberg from 19 to 23 April 2027.
Follow us:
• Newsletter: https://2027.pycon.de/newsletter/
• LinkedIn: https://www.linkedin.com/company/pyconde
• X: https://www.x.com/pyconde
Links:
• Conference website: http://pycon.de
• Other sessions: https://2026.pycon.de/talks/
The conference was organized by
• Python Softwareverband e.V.: http://pysv.org
• Pioneers Hub gemeinnützige GmbH: http://pioneershub.org
in collaboration with NumFOCUS Inc.: http://numfocus.org
If you enjoyed this session, please like, and subscribe to our channel for more insightful talks and discussions.
Share this video with your network to spread the knowledge!
Hashtags:
#Python #PyConDE #PyData #OpenSource #AI #DataScience #MachineLearning #SoftwareEngineering #LLMs #Community #Sovereignty
Acknowledgements:
Special thanks to all the volunteers and sponsors who made this event possible.
About:
Python Softwareverband e.V.:
PySV is a non-profit that promotes the use and development of Python in Germany through events, education, and advocacy, fostering an open Python community.
Pioneers Hub gemeinnützige GmbH:
is a non-profit fostering innovation in AI and tech by connecting experts and promoting knowledge exchange through events and collaborative initiatives.
NumFOCUS Inc.
supports open-source scientific computing by providing financial and logistical support to key projects like NumPy and Jupyter, promoting sustainable development and collaboration.
www.pydata.org
PyData is an educational program of NumFOCUS, a 501(c)3 non-profit organization in the United States. PyData provides a forum for the international community of users and developers of data analysis tools to share ideas and learn from each other. The global PyData network promotes discussion of best practices, new approaches, and emerging technologies for data management, processing, analytics, and visualization. PyData communities approach data science using many languages, including (but not limited to) Python, Julia, and R.")
