Build vocabulary script

[ghost]

Thanks for tensorflow nmt project that makes it easy for me to help my research. And I find it difficult to build vocabulary unless I download the data you provide. So I implement a very simple script to build vocabulary which is easy for newcomer to use this system.

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[ghost]

I signed it !

[googlebot]

CLAs look good, thanks!

[Sabyasachi18]

Hi @Goffic ...
I have a question..
I want to run incremental training on my trained German-English NMT Engine with subword BPE encoding .
Can I update my vocab file with new words from the incremental training data. If Yes, then kindly let me know the process.

Should I append the new words at the end of the existing vocabulary file while running incremental training?
Or should i do a sorting of the vocab file after appending the new words to it?