Data Types & I/O

Commonly-used data types (with Python examples) include:

Name	Python Syntax	Example	Description
String	str()	"Hello World!"	String of characters
Integer	int()	7	Whole number
Float	float()	1.5	Decimal number, or number with floating point values
Boolean	bool()	True	Two-state system that typically represents true/false values
Nothing/Null/NoneType	NoneType	None	No value

For more on data types in Python:

• W3Schools, Python Data Types

Numbers

An integer is a whole number that does not include any decimal (or fractional) values. A float data type includes decimal (or fractional) values.

# printing an integer
print(3)

# storing an integer to a variable
number = 3

# show number variable type
print(type(number))

# print number variable
print(number)

# printing a decimal or float value
print(3.5)

# store float value to a variable
number = 3.5

# show number variable type
print(type(number))

# print number variable
print(number)

Strings

A string is a sequence of characters (letters, numbers, symbols, etc.) We can assign strings to a variable (i.e. store them as a variable).

# assign string to variable
s = "Hello world!"

# show variable type
print(type(s))

# print variable
print(s)

<class 'str'>
Hello world!

Input & Output (I/O)

In programming languages and computing more broadly, I/O stands for Input and Output. Programming languages can take a variety of inputs (user-provided values, data, files, etc) and return outputs in a variety of formats (data stored in memory, output that shows up in the console, newly-created or -modified files, etc).

We’ve already seen I/O in action in Python via print() statements. One way Python accepts input is via the input() function, which accepts a user input and assigns that to a variable.

A sample program that asks a user to enter their name:

# initial prompt
print("Enter your name: ")

# input function
name = input()

# output statement
print("Hello, " + name)

We can modify that program to include the initial prompt as part of the input() statement.

# initial prompt with input function
name = input("Enter your name: ")

# output
print("Hello, " + name)

NOTE: The default data type for a variable created using the input() function is a string object.

For more background on I/O in Python:

• Elements of Computing I “Python Intro” lab