By using pip:

$ pip install pyftpdlib

From sources:

$ git clone
$ cd pyftpdlib
$ python install

You might want to run tests to make sure pyftpdlib works:

$ make test
$ make test-contrib

Additional dependencies

PyOpenSSL, to support FTPS:

$ pip install PyOpenSSL

pysendfile, if you’re on UNIX, in order to speedup uploads (from server to client):

$ pip install pysendfile