Numbers, strings, lists, dictionaries, tuples, files, and sets are generally considered to be the core object (data) types. Types, None, and Booleans are sometimes classified this way as well. There are multiple number types (integer, floating point, complex, fraction, and decimal) and multiple string types (simple strings and Unicode strings in Python 2.X, and text strings and byte strings in Python 3.X).

They are known as “core" types because they are part of the Python language itself and are always available; to create other objects, you generally must call functions in imported modules. Most of the core types have specific syntax for generating the objects: 'spam', for example, is an expression that makes a string and determines the set of operations that can be applied to it. Because of this, core types are hardwired into Python's syntax. In contrast, you must call the built-in open function to create a file object (even though this is usually considered a core type too).

An “immutable" object is an object that cannot be changed after it is created. Numbers, strings, and tuples in Python fall into this category. While you cannot change an immutable object in place, you can always make a new one by running an expression. Bytearrays in recent Pythons offer mutability for text, but they are not normal strings, and only apply directly to text if it's a simple 8-bit kind (e.g., ASCII).

A “sequence" is a positionally ordered collection of objects. Strings, lists, and tuples are all sequences in Python. They share common sequence operations, such as indexing, concatenation, and slicing, but also have type-specific method calls. A related term, “iterable," means either a physical sequence, or a virtual one that produces its items on request.

The term “mapping" denotes an object that maps keys to associated values. Python's dictionary is the only mapping type in the core type set. Mappings do not maintain any left-to-right positional ordering; they support access to data stored by key, plus type-specific method calls.

“Polymorphism" means that the meaning of an operation (like a +) depends on the objects being operated on. This turns out to be a key idea (perhaps the key idea) behind using Python well—not constraining code to specific types makes that code automatically applicable to many types.

Functions for obtaining the square root, as well as pi, tangents, and more, are available in the imported math module. To find a number's square root, import math and call math.sqrt(N). To get a number's square, use either the exponent expression X ** 2 or the built-in function pow(X, 2). Either of these last two can also compute the square root when given a power of 0.5 (e.g., X ** .5).

The int(N) and math.trunc(N) functions truncate, and the round(N, digits) function rounds. We can also compute the floor with math.floor(N) and round for display with string formatting operations.

The float(I) function converts an integer to a floating point; mixing an integer with a floating point within an expression will result in a conversion as well. In some sense, Python 3.X / division converts too—it always returns a floating-point result that includes the remainder, even if both operands are integers.

The oct(I) and hex(I) built-in functions return the octal and hexadecimal string forms for an integer. The bin(I) call also returns a number's binary digits string in Pythons 2.6, 3.0, and later. The % string formatting expression and format string method also provide targets for some such conversions.