ZhouW questions

• Pandas: Replace all 0's in first row with next non-zero value in column?
• how to debug "factor has new levels" error for linear model and prediction [duplicate]
• Google Colab: How to loop through images in a folder?
• Using Handoff with Watchkit to bring the iPhone app to the foreground
• Windows: Z3Exception("init(Z3_LIBRARY_PATH) must be invoked before using Z3-python")

ZhouW answers