from pptx import Presentation

NUMBER_OF_SLIDES = 1000
SLD_LAYOUT_TITLE_AND_CONTENT = 1

prs = Presentation()
slide_layout = prs.slide_layouts[SLD_LAYOUT_TITLE_AND_CONTENT]

for index in range(NUMBER_OF_SLIDES):
    slide = prs.slides.add_slide(slide_layout)
    for placeholder in slide.placeholders:
        placeholder.text = 'Slide {}'.format(index + 1)

prs.save('output.pptx')