Excerpt:
file = open("D:\\DownloadFolder\\test.mp3", "wb")
def callback(data):
file.write(data)
sizeWritten += len(data)
print(sizeWritten)
connect.retrbinary('RETR test.mp3', callback)
print("completed")
Python obviously complains that I didn't define sizeWritten
, but I'm not sure where I should define it. If I put sizeWritten = 0
before the function it still gives an error local variable 'sizeWritten referenced before assignment
. How should I do this?
If it is okay for sizeWritten
to be a global (eg there is only ever going to be one callback active at a time), you can mark it as such in your function:
file = open("D:\\DownloadFolder\\test.mp3", "wb")
sizeWritten = 0
def callback(data):
global sizeWritten
file.write(data)
sizeWritten += len(data)
print(sizeWritten)
and any assignments to the name in callback
alter the global.
In Python 3, you can also use a closure, and the nonlocal
keyword:
def download(remote, local):
file = open(local, "wb")
sizeWritten = 0
def callback(data):
nonlocal sizeWritten
file.write(data)
sizeWritten += len(data)
print(sizeWritten)
connect.retrbinary('RETR ' + remote, callback)
print("completed")
This encapsulates the sizeWritten
and file
objects in a local namespace, at least.
However, you could get the same information directly from the open file
file object:
def callback(data):
file.write(data)
print(file.tell())
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