StringIO.getvalue return content of StringIO:

>>> import StringIO
>>> f = StringIO.StringIO()
>>> f.write('asdf')
>>> f.getvalue()
'asdf'

Alternatively, you can change position of the file using seek:

>>> f.read()
''
>>> f.seek(0)
>>> f.read()
'asdf'

Try following:

mf = StringIO.StringIO()
with zipfile.ZipFile(mf, mode='w', compression=zipfile.ZIP_DEFLATED) as zf:
    zf.writestr('file1.txt', "hi")
    zf.writestr('file2.txt', "hi")

with open("C:/path/my_zip.zip", "wb") as f: # use `wb` mode
    f.write(mf.getvalue())

It is strongly advised to use a context manager. As an advantage, it is made sure the file is always closed, no matter what:

with open("Output.txt", "w") as text_file:
    text_file.write("Purchase Amount: %s" % TotalAmount)

This is the explicit version (but always remember, the context manager version from above should be preferred):

text_file = open("Output.txt", "w")
text_file.write("Purchase Amount: %s" % TotalAmount)
text_file.close()

If you're using Python2.6 or higher, it's preferred to use str.format()

with open("Output.txt", "w") as text_file:
    text_file.write("Purchase Amount: {0}".format(TotalAmount))

For python2.7 and higher you can use {} instead of {0}

In Python3, there is an optional file parameter to the print function

with open("Output.txt", "w") as text_file:
    print("Purchase Amount: {}".format(TotalAmount), file=text_file)

Python3.6 introduced f-strings for another alternative

with open("Output.txt", "w") as text_file:
    print(f"Purchase Amount: {TotalAmount}", file=text_file)

The ZipFile.writestr method writes files from Python string in binary mode. All text files added with this method must then have explicit '\r\n' line endings for Windows programs to read them correctly afterwards.

Your original content had 'universal line ending' within python, which usually only turn into CRLF ('\r\n') when going through a text-mode output file.

That seems to be fixed in python 3.x

Try to open your file with utf-8

import codecs
f = codecs.open("test", "w", "utf-8")

You can ignore the coding error (not recommended) by

f = codecs.open("test", "w", "utf-8", errors='ignore')

Using utils::zip which comes with base R, so usually no need to load library(utils).

writeLines(mytext, "a.txt")
zip(zipfile="filename.zip", files="a.txt", flags="-u -9")

• -u update: only changed or new files (i.e., appends)
• -9 compress better (i.e., DEFLATE)

Note: unzip -v filename.zip in console shows "Stored" under Method unless compression is beneficial, in which case it shows sth like "Defl:X".

If you want to remove the interim file, you can use unlink("a.txt").