How to check the uploaded file is csv or xls in python?

Question

How to check is upload file is CSV or XLS . How to check it in python. I'm importing a file to a binary field in openerp which can be retrived as a binary object. I need to read the file and import the data to a table. User can upload csv or xls file. By knowing only I can use the csv package or xlrd package.

Answer 1

The hex signature for an .xls file is the following:

Excel spreadsheet subheader (MS Office)

09 08 10 00 00 06 05 00 [512 byte offset]

You can read about the other various signatures on Wikipedia.

I believe that you can do something like this. This is untested, but you can fiddle around with it until it works. Please leave comments for any suggestions or changes. Thanks!

xls_sig = b'\x09\x08\x10\x00\x00\x06\x05\x00'
offset = 512
size = 8

with open('spreadsheet.xls', 'rb') as f:
    f.seek(offset)       # Seek to the offset.
    bytes = f.read(size) # Capture the specified number of bytes.

    if bytes == xls_sig:
        print 'Uploaded file is an xls.'
    else:
        print 'File is not an xls.'

Update 1

Tested this and I can verify that it works for detecting .xls files.

Update 2

I developed a program to determine if the file is an xls or xlsx:

import codecs

xlsx_sig = b'\x50\x4B\x05\06'
xls_sig = b'\x09\x08\x10\x00\x00\x06\x05\x00'

filenames = [
    ('spreadsheet.xls', 0, 512, 8),
    ('spreadsheet.xlsx', 2, -22, 4)]

for filename, whence, offset, size in filenames:
    with open(filename, 'rb') as f:
        f.seek(offset, whence) # Seek to the offset.
        bytes = f.read(size)   # Capture the specified number of bytes.

        print codecs.getencoder('hex')(bytes)

        if bytes == xls_sig:
            msg = '"{}" is an xls.'
        elif bytes == xlsx_sig:
            msg = '"{}" is an xlsx.'
        else:
            msg = '"{}" is not an Excel document.'
        print msg.format(filename)

Here is the output:

('0908100000060500', 8)
"spreadsheet.xls" is an xls.
('504b0506', 4)
"spreadsheet.xlsx" is an xlsx.