from PyQt5 import QtWidgets
import pandas as pd

class PandasGUI(QtWidgets.QMainWindow):
    def __init__(self, **kwargs):

        # Property initialization
        self.df_dicts = {}
        self.some_other_property = 5

        super().__init__()
        # This ensures there is always a reference to this widget and it doesn't get garbage collected
        self._reference = self

        for i, (df_name, df_object) in enumerate(kwargs.items()):
            self.df_dicts[df_name] = {}
            self.df_dicts[df_name]['dataframe'] = pd.DataFrame([1,2,3])

        # If you comment out this print statement you get 5 windows
        print(self.df_dicts)

        self.show()

# Create 5 PandasGUI windows
app = QtWidgets.QApplication([])
for i in range(5):
    test_dataframe = pd.DataFrame([1,2,3])
    PandasGUI(test = test_dataframe)

app.exec_()