You can use both , the important thing is which one you can use better . If you think you can use Python better then use Python and in my opinion more people use Python for Blockchain and Python is easier to use than Javascript .
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Creating Blockchain using Python , mining new blocks, and displaying the whole blockchain: The data will be stored in JSON format which is very easy to implement and easy to read. The data is stored in a block and the block contains multiple data.
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