How do I reverse the order of the pages in a pdf file using pyPdf?

I have a pdf file "myFile.pdf". I would like to reverse the order of its pages using pyPdf开发者_如何学C. How?

from pyPdf import PdfFileWriter, PdfFileReader
output_pdf = PdfFileWriter()

with open(r'input.pdf', 'rb') as readfile:
    input_pdf = PdfFileReader(readfile)
    total_pages = input_pdf.getNumPages()
    for page in xrange(total_pages - 1, -1, -1):
        output_pdf.addPage(input_pdf.getPage(page))
    with open(r'output.pdf', "wb") as writefile:
        output_pdf.write(writefile)

Thanks for sharing suggestions. I used them and edited a bit to make the interface more graphical when selecting and saving a file. New to all of this and what I added might not be efficient or clean, but it worked for me and thought to share.

from PyPDF2 import PdfFileWriter, PdfFileReader
import tkinter as tk
from tkinter import filedialog
import ntpath
import os


output_pdf = PdfFileWriter()

# grab the location of the file path sent
def path_leaf(path):
    head, tail = ntpath.split(path)
    return head

# graphical file selection
def grab_file_path():
    # use dialog to select file
    file_dialog_window = tk.Tk()
    file_dialog_window.withdraw()  # hides the tk.TK() window
    # use dialog to select file
    grabbed_file_path = filedialog.askopenfilename()
    return grabbed_file_path


# file to be reversed
filePath = grab_file_path()

# open file and read
with open(filePath, 'rb') as readfile:
    input_pdf = PdfFileReader(readfile)

    # reverse order one page at time
    for page in reversed(input_pdf.pages):
        output_pdf.addPage(page)

    # graphical way to get where to select file starting at input file location
    dirOfFileToBeSaved = path_leaf(filePath)
    locationOfFileToBeSaved=filedialog.asksaveasfilename(initialdir=dirOfFileToBeSaved, initialfile='name of reversed file.pdf',title="Select or type file name and location", filetypes=[("pdf files", "*.pdf")])
    # write the file created
    with open(locationOfFileToBeSaved, "wb") as writefile:
        output_pdf.write(writefile)

# open the file when done
os.startfile(locationOfFileToBeSaved)

As of (long before) January 2019, pyPdf is no longer updated, and upon testing is not compatible with (at least) Python 3.6, and likely at all with Python 3:

In [1]: import pyPdf
---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
<ipython-input-1-bba5a42e9137> in <module>
----> 1 import pyPdf

c:\temp\envminecart\lib\site-packages\pyPdf\__init__.py in <module>
----> 1 from pdf import PdfFileReader, PdfFileWriter
      2 __all__ = ["pdf"]

ModuleNotFoundError: No module named 'pdf'

(Moving the __all__ assignment above the import fixes this specific problem, but other SyntaxErrors due to Python 2 syntax then pop up.)

Fortunately, its successor project, PyPDF2, works cleanly on Python 3.6 (at least). It appears the core user-facing API was intentionally maintained to be compatible with pyPdf, so nosklo's answer can be used in modern Python after a pip install PyPDF2 just by changing to PyPDF2 in the import statement, and switching xrange to range:

from PyPDF2 import PdfFileWriter, PdfFileReader
output_pdf = PdfFileWriter()

with open(r'input.pdf', 'rb') as readfile:
    input_pdf = PdfFileReader(readfile)
    total_pages = input_pdf.getNumPages()
    for page in range(total_pages - 1, -1, -1):
        output_pdf.addPage(input_pdf.getPage(page))
    with open(r'output.pdf', "wb") as writefile:
        output_pdf.write(writefile)

I would also recommend the more Pythonic approach of just iterating over the pages directly using reversed:

from PyPDF2 import PdfFileWriter, PdfFileReader

output_pdf = PdfFileWriter()

with open('input.pdf', 'rb') as readfile:
    input_pdf = PdfFileReader(readfile)

    for page in reversed(input_pdf.pages):
        output_pdf.addPage(page)

    with open('output.pdf', "wb") as writefile:
        output_pdf.write(writefile)

I don't know if this .pages collection was available in the original pyPdf, but arguably it doesn't really matter much at this point.