Welcome to Python for Neuroimaging!

A brief history

Python is a high-level, interpreted language created by Guido van Rossum.

2 to 3

Python has undergone three major revisions since it's initial release back in 1991. The most recent revision was Python 2 to 3. It is recommended that you use Python 3.

Python 2 still exists, but was officially deprecated on January 1st, 2020.

The interpreter

Instead of having to compile source code into machine code, Python uses an interpreter to execute your code one line at a time.

starting the interpreter

Python should be installed by default on most Linux and macOS systems. For Windows, you should consider installing Python through the Windows Subsystem for Linux. To start the interpreter, open a terminal and type python3 at the command prompt and hit Enter

% python3
Python 3.8.2 (default, Mar 26 2020, 15:43:04) 
[Clang 11.0.3 (clang-1103.0.32.29)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 

Command not found

If you receive a command not found error, either your system does not have Python installed, or your environment is misconfigured. Try logging into a FASSE host and use one of the existing Python modules

module load ncf miniconda3/py39_4.11.0-ncf

If that doesn't work, contact a system administrator.

executing statements

You can execute statements interactively by typing a statement at the prompt >>> and pressing Enter

>>> 1 + 1
2
>>>

Python will read the input statement, evaluate (execute) it, print the result, and loop back to the command prompt. This is known as a read-eval-print-loop or REPL.

comments

In Python, comments begin with a hash # character and will be ignored by the interpreter

>>> # this is a comment

For multi-line comments, you can use multiple hash # characters or triple quotation marks (single or double quotes work)

"""
I am
a multiline
comment
"""

quitting

To quit the Python interpreter, type Control + D or execute the quit() or exit() functions

>>> quit()