Showing a Progress Bar in a QMainWindow from a Callback, boto3.s3

Question

I am creating a program that uploads a folder into a bucket. Right now I have the program and UI all set I would just like to add a progress bar showing which file is being uploaded.

I am wondering if there is a way to use the s3.upload_file(fileName, bucketName, objectName, Callback=ProgressPercentage(path.text())) to get a progress bar on my QMainWindow. Or if I need to go about this a different way.

class ProgressPercentage(object):
    def __init__(self, filename):
        self._filename = filename
        self._size = float(os.path.getsize(filename))
        self._seen_so_far = 0
        self._lock = threading.Lock()

    def __call__(self, bytes_amount):
        # To simplify, assume this is hooked up to a single filename
        with self._lock:
            self._seen_so_far += bytes_amount
            percentage = (self._seen_so_far / self._size) * 100
            sys.stdout.write(
                "\r%s  %s / %s  (%.2f%%)" % (
                    self._filename, self._seen_so_far, self._size,
                    percentage))
            sys.stdout.flush()

I think you've almost got it done. Just remember to operate GUI in main eventloop and it would be fine. — ToSimplicity, Jun 16 '20 at 20:35

score 2 · Accepted Answer · answered Jun 16 '20 at 20:55

The logic in this case is to create a QObject that has a signal that indicates the progress, in addition the upload task must be executed in a secondary thread so that the GUI does not freeze:

import math
import os
import sys
import threading

import boto3

from PyQt5 import QtCore, QtWidgets


class S3Worker(QtCore.QObject):
    started = QtCore.pyqtSignal()
    finished = QtCore.pyqtSignal()
    percentageChanged = QtCore.pyqtSignal(int)

    def __init__(self, parent=None):
        super().__init__(parent)

        self._s3 = boto3.client("s3")

    @property
    def s3(self):
        return self._s3

    def upload(self, filename, bucketname, objectname):
        self._size = float(os.path.getsize(filename))
        self._seen_so_far = 0
        threading.Thread(
            target=self._execute, args=(filename, bucketname, objectname), daemon=True
        ).start()

    def _execute(self, fileName, bucketName, objectName):
        self.started.emit()
        self.s3.upload_file(fileName, bucketName, objectName, Callback=self._callback)
        self.finished.emit()

    def _callback(self, bytes_amount):
        self._seen_so_far += bytes_amount
        percentage = (self._seen_so_far / self._size) * 100
        self.percentageChanged.emit(math.floor(percentage))


class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.filename_le = QtWidgets.QLineEdit()
        self.upload_btn = QtWidgets.QPushButton("Upload")
        self.percentage_pb = QtWidgets.QProgressBar()

        lay = QtWidgets.QGridLayout(self)
        lay.addWidget(QtWidgets.QLabel("filename:"))
        lay.addWidget(self.filename_le, 0, 1)
        lay.addWidget(self.upload_btn, 0, 2)
        lay.addWidget(self.percentage_pb, 1, 0, 1, 3)

        self.qs3 = S3Worker()

        self.upload_btn.clicked.connect(self.start_upload)
        self.qs3.started.connect(lambda: self.upload_btn.setEnabled(False))
        self.qs3.finished.connect(lambda: self.upload_btn.setEnabled(True))
        self.qs3.percentageChanged.connect(self.percentage_pb.setValue)

    def start_upload(self):
        filename = self.filename_le.text()
        if os.path.exists(filename):
            self.qs3.upload(filename, "mybucket", "foobject")


def main():
    app = QtWidgets.QApplication(sys.argv)

    w = Widget()
    w.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Thank you for the help! My only problem now is the progress bar stops at 19% whenever I upload a file. Any ideas on why that is? — Ganzatron, Jun 17 '20 at 16:35

Showing a Progress Bar in a QMainWindow from a Callback, boto3.s3

1 Answers1