The EDF standard was introduced in 1992. The extension of EDF with annotations was first described in 1998 and more formalized with the EDF+ standard that was published in 2003. The EDF website describes both standards and discusses implementation details.
pyedf is a python package to read from and write EEG data to EDF/EDF+ files.
Since EDF is such a widely used format, there exist multiple Python implementations for reading and writing EDF files. However, most of these Python modules consist of wrappers around the C-code implementation edflib, which makes installation more cumbersome and reduces portability. This implementation is in pure python with limited dependencies on external packages while having support for Python 2.7 and 3.x.
The edf file, included for testing, is taken from EDFBrowser Test Files.