import sys

# program run correctly, if import PyQt5 here before import matplotlib
# from PyQt5.QtWidgets import QApplication, QVBoxLayout, QWidget 
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure
# program will raise TypeError, if import import PyQt5 after import matplotlib
from PyQt5.QtWidgets import QApplication, QVBoxLayout, QWidget

if __name__ == "__main__":
    app = QApplication(sys.argv)
    # init figure
    fig = Figure()
    fig_canvas = FigureCanvas(fig)
    # init widget
    layout = QVBoxLayout()
    layout.addWidget(fig_canvas) # TypeError here, if import PyQt5 after import matlpotlib
    win = QWidget()
    win.setLayout(layout)
    # run
    win.show()
    sys.exit(app.exec())