Gain insights into Python 3's new syntax, data types, strings, bytes, and iterators through interactive coding samples. Upgrade your Python skills with hands-on, real-time code modifications.

Are you ready to take the plunge into Python 3? You might be just getting started with Python or you might be someone who understands Python2 and now wants to upgrade to Python 3. This course is designed to help you achieve your goal faster.

Learn about the new syntax, data types, strings, bytes, iterators and much more with interactive coding samples. Execute code using interactive playgrounds, modify the code to see your changes in action and get yourself upgraded to the newest version of Python that is here to stay for a while.

This course is derived from Dive into Python 3 by Mark Pilgrim. See License for more details.
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Python 3: An interactive deep dive

Before this goes any further, I want to briefly mention the library search path. Python looks in several places when you try to import a module. Specifically, it looks in all the directories defined in `sys.path`. This is just a list, and you can easily view it or modify it with standard list methods. (You’ll learn more about lists in Native Datatypes.)

import sys                                                         #①

print (sys.path)                                                   #②
#['/usercode', 
# '/usr/lib/python3.4', 
# '/usr/lib/python3.4/plat-x86_64-linux-gnu', 
# '/usr/lib/python3.4/lib-dynload', 
# '/usr/local/lib/python3.4/dist-packages', 
# '/usr/lib/python3/dist-packages']

print (sys)                                                        #③
#<module 'sys' (built-in)>

print (sys.path.insert(0, '/home/mark/diveintopython3/examples'))  #④
#None

print (sys.path)                                                   #⑤
#['/home/mark/diveintopython3/examples', 
#'/usercode', 
#'/usr/lib/python3.4', 
#'/usr/lib/python3.4/plat-x86_64-linux-gnu', 
#'/usr/lib/python3.4/lib-dynload', 
#'/usr/local/lib/python3.4/dist-packages', 
#'/usr/lib/python3/dist-packages']


①	Importing the `sys` module makes all of its functions and attributes available.

②	`sys.path` is a list of directory names that constitute the current search path. (Yours will look different, depending on your operating system, what version of Python you’re running, and where it was originally installed.) Python will look through these directories (in this order) for a `.py` file whose name matches what you’re trying to import.

③	Actually, I lied; the truth is more complicated than that, because not all modules are stored as `.py` files. Some are `built-in modules`; they are actually baked right into Python itself. Built-in modules behave just like regular modules, but their Python source code is not available, because they are not written in Python! (Like Python itself, these built-in modules are written in C.)

④	You can add a new directory to Python’s search path at runtime by adding the directory name to `sys.path`, and then Python will look in that directory as well, whenever you try to import a module. The effect lasts as long as Python is running.

⑤	By using `sys.path.insert(0, new_path)`, you inserted a new directory as the first item of the `sys.path` list, and therefore at the beginning of Python’s search path. This is almost always what you want. In case of naming conflicts (for example, if Python ships with version 2 of a particular library but you want to use version 3), this ensures that your modules will be found and used instead of the modules that came with Python.

Your First Python Program

Native Datatypes

Comprehensions

Strings

Regular Expressions

Closures & Generators

Classes & Iterators

Advanced Iterators

Unit Testing

Refactoring

Files

XML

Serializing Python Objects

HTTP Web Services

Case Study: Porting chardet to Python 3

Packaging Python Libraries

Appendix : Where To Go From Here

The import Search Path