How to start working with blk*.dat data? I have the complete bitcoins block data (blk00000.dat, blk00001.dat.....). I want to convert it into some readable format like csv or json. Can it be done using python or any other software ?
You can use Bitcoin-ABE

https://github.com/bitcoin-abe/bitcoin-abe

There are various options, I used the sqlite export to get a local SQL database with blocks, tx, outputs etc.