Amit Saha: tempfile.NamedTemporaryFile() in Python

In Python, when you need to create a temporary file with a filename associated to it on disk, NamedTemporaryFile function in the tempfile module is the goto function. Here are some use cases that I think one might use it for.

Case #1: You simply need a named empty temporary file

You just want a file object (pointing to an empty file) which has a filename associated to it and hence you cannot use a StringIO object:

from tempfile import NamedTemporaryFile
f = NamedTemporaryFile()

# use f
..

Once f is garbage collected, or closed explicitly, the file will automatically be removed from disk.

Case #2: You need a empty temporary file with a custom name

You need a temporary file, but want to change the filename to something you need:

from tempfile import NamedTemporaryFile
f = NamedTemporaryFile()

# Change the file name to something
f.name = 'myfilename.myextension'

# use f

Since you change the name of the file, this file will automatically not be removed from disk when you close the file or the file object is garbage collected. Hence, you will need to do so yourself:

from tempfile import NamedTemporaryFile
f = NamedTemporaryFile()

# Save original name (the "name" actually is the absolute path)
original_path = f.name

# Change the file name to something
f.name = 'myfilename.myextension'

# use f

..

# Remove the file
os.unlink(original_path)
assert not os.path.exists(original_path)

Case #3: You need a temporary file, write some contents, read from it later

This use case is where you need a temporary file, but you want to work with it like a "normal" file on disk - write something to it and later, read it from it. In other words, you just want to control when the file gets removed from disk.

from tempfile import NamedTemporaryFile
# When delete=False is specified, this file will not be
# removed from disk automatically upon close/garbage collection
f = NamedTemporaryFile(delete=False)

# Save the file path
path = f.name

# Write something to it
f.write('Some random data')

# You can now close the file and later
# open and read it again
f.close()
data = open(path).read()

# do some work with the data

# Or, make a seek(0) call on the file object and read from it
# The file mode is by default "w+" which means, you can read from
# and write to it.
f.seek(0)
data = f.read()

# Close the file
f.close()

..

# Remove the file
os.unlink(path)
assert not os.path.exists(path)

By default delete is set to True when calling NamedTemporaryFile(), and thus setting it to False gives more control on when the file gets removed from disk.