Create temporary files and directories using tempfile

Python tempfile module allows you to create a temporary file and perform various operations on it. Temporary files may be required when we need to store data temporarily during the program’s execution or when we are working with a large amount of data. These files are created with unique names and stored in a platform-dependent default location. The files created using tempfile module are deleted as soon as they are closed. 

In this tutorial, we will cover how to create and edit temporary files:

Creating a Temporary File

The file is created using the TemporaryFile() function of the tempfile module. By default, the file is opened in w+b mode, that is, we can both read and write to the open file. Binary mode is used so that files can work with all types of data. This file may not have a proper visible name in the file system.

Example:

Python3

import tempfile

temp = tempfile.TemporaryFile()
print(temp)
print(temp.name)

Output:

<_io.BufferedRandom name=7>
7

The function returns a file-like object that can be used as a temporary storage area. name attribute is used to get the random and unique name of the file. 

Note: This is not an actual visible filename and there is no reference to this file in the file system.

Creating a Named Temporary File

The NamedTemporaryFile() function creates a file in the same way as TemporaryFile() but with a visible name in the file system. It takes a delete parameter which we can set as False to prevent the file from being deleted when it is closed.

Example:

Python3

import tempfile

temp = tempfile.NamedTemporaryFile()
print(temp)
print(temp.name)

Output:

<tempfile._TemporaryFileWrapper object at 0x7f77d332f6d8>
/tmp/tmprumbbjz4

This also returns a file-like object as before, the only difference is that the file has a visible name this time. 

Adding a Suffix and a Prefix to a Temporary File

We may choose to add a suffix or prefix to the name of a named temporary file, by specifying the parameters ‘suffix’ and ‘prefix’. 

Example

Python3

import tempfile

temp = tempfile.NamedTemporaryFile(prefix='pre_', suffix='_suf')
print(temp.name)

Output:

/tmp/pre_ddur6hvr_suf

Reading and Writing to a Temporary File

The write() method is used to write to a temporary file. It takes input as binary data by default. We can pass the string to be written as input, preceded by a ‘b’ to convert it to binary data. 

The write function returns the number of characters written. If we open the file in text mode(w+t), we can use the writelines() method instead, which takes a string parameter. After writing to the file, the pointer is at the end of the file. So, before we can read the contents, seek() method is called to set the file pointer at the start of the file. 

seek() takes as argument the index of the character before which we want to place the pointer. The read() function is then used to read the contents.

Example:

Python3

import tempfile

temp = tempfile.TemporaryFile()
temp.write(b'foo bar')
temp.seek(0)
print(temp.read())

temp.close()

Output :

b'foo bar'

Creating a Temporary Directory

Like creating files, we can also create a temporary directory to store our temporary files. The TemporaryDirectory() function is used to create the directory. After we are done working with the temporary files, the directory needs to be deleted manually using os.removedirs().

Example: 

Python3

import tempfile
import os

temp_dir = tempfile.TemporaryDirectory()
print(temp_dir)

Output:

<TemporaryDirectory '/tmp/tmpgjl5ki_5'>

Secure Temporary File and Directory

We can securely create a temporary file using mkstemp(). The file created by this method is readable and writable only by the creating user. We can add prefix and suffix parameters like in NamedTemporaryFile(). The default mode is binary, but we can open it in text mode by setting the ‘text’ parameter as True. This file does not get deleted when closed.

Example:

Python3

import tempfile


secure_temp = tempfile.mkstemp(prefix="pre_",suffix="_suf")
print(secure_temp)

Output:

(71, '/tmp/pre_i5us4u9j_suf')

Similarly, we can create a secure temporary directory using mkdtemp() method.

Example:

Python3

import tempfile

secure_temp_dir = tempfile.mkdtemp(prefix="pre_",suffix="_suf")
print(secure_temp_dir)

Output:

/tmp/pre_9xmtwh4u_suf

Location of Temporary Files

We can set the location where the files are stored by setting the tempdir attribute. The location can be fetched using gettempdir() method. When we create a temporary file or directory, Python searches in a standard list of directories to find one in which the calling user can create files. 

The list in order of preference is :

1. The directory named by the TMPDIR environment variable.
2. The directory named by the TEMP environment variable.
3. The directory named by the TMP environment variable.
4. A platform-specific directory:
   • On Windows, the directories C:\TEMP, C:\TMP, \TEMP, and \TMP, in that order.
   • On all other platforms, the directories /tmp, /var/tmp, and /usr/tmp, in that order.
5. The current working directory.

Example:

Python3

import tempfile

tempfile.tempdir = "/temp"
print(tempfile.gettempdir())

Output:

/temp

We have covered the methods used to create temporary files and directories. We have also covered different operations like creating named temporary files, adding prefixes and suffixes, and setting the location of the temporary files.

Temporary files are a very important concept in Advanced Python programming. Creating and using temporary files will help you in many operations like handling intermediate data, testing, development, etc.