The departure is due to "unforeseen circumstances" and HBO said in a statement that it supports Cochrane's decision, Deadline writes.
Filming of the first season, which is subtitled "Harry Potter and the Philosopher's Stone", is currently underway and the series is expected to premiere this Christmas.
Ginny Weasley is a key character in J.K. Rowling's Harry Potter books because of her close relationship with Harry Potter in the later books.
The lead role of Harry Potter is played by Scottish actor Dominic McLaughlin. Potter's friends Hermione Granger and Ron Weasley are played by Arabella Stanton and Alastair Stout, respectively.
Production on season two begins this fall. It is not known who will take over from Cochrane.
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