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A class for asynchronous url loading using Qt, PyQt
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| ''' | |
| Copyright 2014 Lloyd Konneker | |
| Release under the GPLv3 | |
| ''' | |
| fromPyQt5.QtCoreimportpyqtSignalasSignal | |
| fromPyQt5.QtCoreimportQObject,QByteArray,QUrl | |
| fromPyQt5.QtNetworkimportQNetworkAccessManager,QNetworkRequest | |
| classDownLoader(QObject): | |
| ''' | |
| Asynchronous download from network, which is expected to be unreliable and possibly slow. | |
| A thin wrapper around QNetworkAccessManager() | |
| Qt docs: 'One QNetworkAccessManager should be enough for the whole Qt application.' | |
| Similarly, one DownLoader might be enought for the whole app. | |
| It is untested what happens when you create more than one. | |
| Usage: | |
| foo = Downloader(url) | |
| foo.downloaded.connect(clientLoader) | |
| foo.doDownload(QUrl('http:/...')) | |
| # execution continues, clientLoader slot will receive signal | |
| def clientLoader(): | |
| bar = foo.downloadedData() | |
| # bar is only a reference, consume it before calling doDownload() again | |
| ''' | |
| downloaded=Signal() | |
| def__init__(self):# parent not used | |
| super(DownLoader,self).__init__()# !!! init QObject | |
| # private | |
| self._webController=QNetworkAccessManager() | |
| self._downloadedData=None | |
| # connect asynchronous result, when a request finishes | |
| self._webController.finished.connect(self._fileDownloaded) | |
| # private slot, no need to declare as slot | |
| def_fileDownloaded(self,reply): | |
| ''' | |
| Handle signal 'finished'. A network request has finished. | |
| ''' | |
| self._downloadedData=reply.readAll() | |
| # prior _downloadedData is now garbage collectable | |
| assertisinstance(self._downloadedData,QByteArray) | |
| reply.deleteLater()# schedule for delete from main event loop | |
| # print("emitted") | |
| self.downloaded.emit() | |
| ''' | |
| Public API | |
| ''' | |
| defdoDownload(self,url): | |
| assertisinstance(url,QUrl) | |
| request=QNetworkRequest(url) | |
| self._webController.get(request) | |
| # asynchronous, does not wait, execution continues | |
| defdownloadedData(self): | |
| ''' | |
| QByteArray that was downloaded. | |
| Call this only after receiving signal 'downloaded'. | |
| Copy result before calling doDownload() again. | |
| ''' | |
| returnself._downloadedData | |
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