Master Python Variables and Data Types: From Assignment to Conversion

Variable Assignment

In Python, variable assignment does not require type declaration. Each variable created in memory includes an identifier, name, and data. A variable must be assigned before use; the equal sign (=) assigns a value to the variable, with the left side being the variable name and the right side the stored value.

Example:

counter = 100

miles = 1000.0

name = "John"

Running the program outputs:

100

1000.0

John

Multiple Variable Assignment

Python allows assigning the same value to several variables simultaneously: a = b = c = 1 This creates a single integer object with value 1, and all three variables reference the same memory.

Different values can also be assigned to multiple variables: a, b, c = 1, 2, "john" Here, integers 1 and 2 are assigned to a and b, and the string "john" to c.

Standard Data Types

Python defines five standard data types for storing various kinds of data:

Numbers

String

List

Tuple

Dictionary

Numbers

Numeric types store numeric values and are immutable; changing a number creates a new object.

Creating numbers:

var1 = 1

var2 = 10

Delete references with del:

del var1

del var_a, var_b

Python supports four numeric types:

int (signed integer)

long (long integer, also represents octal and hexadecimal)

float (floating‑point)

complex (complex number)

Strings

A string is a sequence of characters, numbers, or underscores, written as s = "a1a2...an". Substrings can be obtained using slicing s[start:end], where indices may be positive or negative.

Example:

s = 'ilovepython'

s[1:5]

yields love.

Concatenation uses + and repetition uses *.

Lists

Lists are the most frequently used mutable sequence type, defined with square brackets [ ]. They can contain heterogeneous elements, including other lists.

List slicing works like string slicing: list[start:end]. Concatenation uses + and repetition uses *.

Tuples

Tuples are immutable sequences defined with parentheses ( ). Elements are separated by commas. Because they cannot be modified, they are often used for read‑only data.

Dictionaries

Dictionaries are unordered collections of key‑value pairs, defined with braces { }. Keys are used for lookup instead of numeric indices.

Data Type Conversion

Built‑in functions can convert between types, returning a new object: int(x[, base]): Convert x to an integer. long(x[, base]): Convert x to a long integer. float(x): Convert x to a floating‑point number. complex(real[, imag]): Create a complex number. str(x): Convert x to a string. repr(x): Return a string representation of x. eval(str): Evaluate a Python expression contained in a string. tuple(s): Convert a sequence to a tuple. list(s): Convert a sequence to a list. set(s): Convert to a mutable set. dict(d): Create a dictionary from a sequence of (key, value) pairs. frozenset(s): Convert to an immutable set. chr(x): Convert an integer to a character. unichr(x): Convert an integer to a Unicode character. ord(x): Convert a character to its integer code point. hex(x): Convert an integer to a hexadecimal string. oct(x): Convert an integer to an octal string.