Core Python Programming (2nd Edition)

2.6. Numbers

Python supports five basic numerical types, three of which are integer types.

• int (signed integers)

  • long (long integers)

  • bool (Boolean values)

• float (floating point real numbers)

• complex (complex numbers)

Here are some examples:

int 0101 84 -237 0x80 017 -680 -0X92 long 29979062458L -84140l 0xDECADEDEADBEEFBADFEEDDEAL bool True False float 3.14159 4.2E-10 -90. 6.022e23 -1.609E-19 complex 6.23+1.5j -1.23-875J 0+1j 9.80665-8.31441J -.0224+0j

Numeric types of interest are the Python long and complex types. Python long integers should not be confused with C longs. Python longs have a capacity that surpasses any C long. You are limited only by the amount of (virtual) memory in your system as far as range is concerned. If you are familiar with Java, a Python long is similar to numbers of the BigInteger class type.

Moving forward, ints and longs are in the process of becoming unified into a single integer type. Beginning in version 2.3, overflow errors are no longer reportedthe result is automagically converted to a long. In a future version of Python, the distinction will be seamless because the trailing "L" will no longer be used or required.

Boolean values are a special case of integer. Although represented by the constants true and False, if put in a numeric context such as addition with other numbers, true is treated as the integer with value 1, and False has a value of 0.

Complex numbers (numbers that involve the square root of -1, so-called "imaginary" numbers) are not supported in many languages and perhaps are implemented only as classes in others.

There is also a sixth numeric type, decimal, for decimal floating numbers, but it is not a built-in type. You must import the decimal module to use these types of numbers. They were added to Python (version 2.4) because of a need for more accuracy. For example, the number 1.1 cannot be accurately representing with binary floating point numbers (floats) because it has a repeating fraction in binary. Because of this, numbers like 1.1 look like this as a float:

>>> 1.1 1.1000000000000001 >>> print decimal.Decimal('1.1') 1.1

All numeric types are covered in Chapter 5.