Data Types

• In Python 3, as in previous versions, every value has a data type. Python 3 works out which data type each variable should have, based on its original assignment, and keeps track of the data type internally. This means that you don’t need to explicitly declare the data type of each variable. Native data types in Python 3 include booleans, which have true or false values, integers, floating point numbers and fractions, strings and more complex types, such as module, function and file.
  
  

Functions

• Python 3 has functions -- named blocks of code that can be executed at different points within a program -- but they are easier to implement than in some other programming languages, such as C++, Java and Pascal. Each function declaration starts with the keyword “def,” followed by the function name, then by one or more arguments in parentheses. Every Python 3 function returns a value; if the function doesn’t explicitly execute a return statement, it returns the Python null value, called “none.”
  
  

Print() Function

• In Python 3, the print statement has been replaced by the print() function, which takes three keyword arguments: “sep,” “end” and “file.” The print() function is used to print program output to the screen or elsewhere. The “sep” argument defaults to a space. The “end” argument defaults to “\n,” which is why calls to the print() function are followed by a new line. The “file” argument defaults to “sys.stdout,” the standard output stream. The new print() function renders print statements in earlier Python programs invalid. However, being statements, they can be replaced reliably using an automated tool.
  
  

Integers

• Python 2 had two separate data types for integers, known as “int” and “long.” The “int” data type was limited by the parameter called “sys.maxint,” which varied from platform to platform, but was usually 2^32-1, while the “long” data type was used for any integer larger than a plain “int.” Python 3 does away with the “long” data type and includes just a single built-in data type for integers, called “int.” The new “int” data type behaves much like the old “long” data type. Although the “sys.maxint” constant has been removed, there is no longer a limit to the value of integers in Python 3.