Python Programming/Data types

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Data types determine whether an object can do something, or whether it just would not make sense. Other programming languages often determine whether an operation makes sense for an object by making sure the object can never be stored somewhere where the operation will be performed on the object (this type system is called static typing). Python does not do that. Instead it stores the type of an object with the object, and checks when the operation is performed whether that operation makes sense for that object (this is called dynamic typing).

Python's basic datatypes are:

• Integers, equivalent to C longs
• Floating-Point numbers, equivalent to C doubles
• Long integers of non-limited length
• Complex Numbers.
• Strings
• Some others, such as type and function

Python's composite datatypes are:

• lists
• tuples
• dictionaries, also called dicts, hashmaps, or associative arrays

Literal integers can be entered as in C:

• decimal numbers can be entered directly
• octal numbers can be entered by prepending a 0 (0732 is octal 732, for example)
• hexadecimal numbers can be entered by prepending a 0x (0xff is hex FF, or 255 in decimal)

Floating point numbers can be entered directly.

Long integers are entered either directly (1234567891011121314151617181920 is a long integer) or by appending an L (0L is a long integer). Computations involving short integers that overflow are automatically turned into long integers.

Complex numbers are entered by adding a real number and an imaginary one, which is entered by appending a j (i.e. 10+5j is a complex number. So is 10j). Note that j by itself does not constitute a number. If this is desired, use 1j.

Strings can be either single or triple quoted strings. The difference is in the starting and ending delimiters, and in that single quoted strings cannot span more than one line. Single quoted strings are entered by entering either a single quote (') or a double quote (") followed by its match. So therefore

'foo' works, and
"moo" works as well,
     but
'bar" does not work, and
"baz' does not work either.
"quux'' is right out.

Triple quoted strings are like single quoted strings, but can span more than one line. Their starting and ending delimiters must also match. They are entered with three consecutive single or double quotes, so

'''foo''' works, and
"""moo""" works as well,
     but
'"'bar'"' does not work, and
"""baz''' does not work either.
'"'quux"'" is right out.

Tuples are entered in parenthesis, with commas between the entries:

(10, 'Mary had a little lamb')

Also, the parenthesis can be left out when it's not ambiguous to do so:

10, 'whose fleece was as white as snow'

Note that one-element tuples can be entered by surrounding the entry with parentheses and adding a comma like so:

('this is a stupid tuple',)

Lists are similar, but with brackets:

['abc', 1,2,3]

Dicts are created by surrounding with curly braces a list of key,value pairs separated from each other by a colon and from the other entries with commas:

{ 'hello': 'world', 'weight': 'African or European?' }

Any of these composite types can contain any other, to any depth:

((((((((('bob',),['Mary', 'had', 'a', 'little', 'lamb']), { 'hello' : 'world' } ),),),),),),)