Page 1

• Data Types

• Vatsal Maru - Assistant Professor of Instruction

• JSOM 4.414

Page 2: Constants

• Fixed values - numbers, letters, and strings

  • print (123) - prints the number 123

  • print (98.6) - prints the number 98.6

  • print ('Hello world') - prints the string 'Hello world'

Transcript Notes

Page 3: Reserve Words

• Reserve words are words that cannot be used as identifiers

• Examples of reserve words:

  • del

  • global

  • not

  • with

  • as

  • elif

  • if

  • or

  • yield

  • assert

  • else

  • import

  • pass

  • break

  • except

  • in

  • raise

  • class

  • finally

  • is

  • return

  • continue

  • for

  • lambda

  • try

  • def

  • from

  • nonlocal

  • while

Page 4: Variables

Main Ideas:

• Variables are used to store data in memory

• Data can be accessed using the variable name

• Variables can be changed later

• Variable names should not be repeated

Supporting Details:

• Variable Examples:

  • x = 5

  • temperature = 70

  • pi = 3.14

  • X = 7

Page 5: Variables in Python

Main Ideas:

• Variable names (identifiers) must start with a letter (or_)

• Variable names are case sensitive

• If the variable names are long, copy and paste is a good practice

Supporting Details:

• Variable names must start with a letter or an underscore (_) character

• Variable names are case sensitive, meaning "x" and "X" are different variables

• Using meaningful variable names can improve code readability

• Copying and pasting long variable names can help avoid typing errors

• Examples of valid variable names: x, temperature, pi

Page 6: Variables

• Variable names are user defined, not predefined

• Best practice is to name variables such that they are self-explanatory

• This improves readability of code and debugging (troubleshooting)

  • hininches = 20

  • h_in_in = 20

  • height_inches = 20

Page 7

• Python Basics Structures

  • y = x*7

  • print(y)

  • Note: 42

• Assignment with expression

  • Type: str

  • Output: 'Hello, World!'

• Variables

  • Variables: X, y, pi

• Error: NameError

  • Operator: *

  • Line: 1

  • Error: name 'pi' is not defined

• Constant

  • Constant: 7, 3.14

• Assignment statement

  • Print statement: 3.14

• Function

  • Functions: print, type

• Usage of variables in functions or programs

  • Without creating a variable, we cannot use them in a function or program

Page 8: Variables

• Variables are used in equations

• Variables are updated based on computations

X = 10

y = 25

X = y * X * 0.5

X = 125

Page 9: Operator Precedence

• Highest to lowest precedence in python

  • Parentheses

  • Exponent (raise to a power)

  • Division

  • Multiplication

  • Remainder

  • Addition

  • Subtraction

• Operations are evaluated from left to right

Page 10: Operator Precedence

• Question: Which operator takes precedence in Python?

• Expression: + 4 * 6 - 8 / 10 ** 2

• Output: 25.92

Page 11: Operator Precedence

• For readability and debugging, use parentheses

• Write the easiest way possible

• Why?

  • Operations might not give errors

  • However, they might not return the intended results if they are computed wrongly in Python

Page 12: Identifier Types

• In programming, we can differentiate variables, constants, or literals

• In python, we have integers, floats, and strings

• To know the type, we can use type() function

• The operators also identify these different types

• For example, + and * operators add and multiply numbers

• + operator can also concatenate strings

• * operator can multiply sequence

Page 13: Identifier Types

• Operators:

  • + operator adds numbers

  • * operator multiplies numbers

• Example:

  • Addition:

    • z = 1 + 2

    • print(z) Output: 3

  • Multiplication:

    • z = 1 * 2

    • print(z) Output: 2

  • String Concatenation:

    • z = "hello " + "world"

    • print(z) Output: hello world

Page 14

• Identifier Types

  • Z = "hello " * "world"

    • Output: TypeError - can't multiply sequence by non-int of type 'str'

  • Z = "this " * 2

    • Output: this this

  • Z = "this" + 1

    • Output: TypeError - can only concatenate str (not "int") to str

Page 15: Type Conversions

• Performing a math operation between integer and float, the resulting variable is automatically converted to a float

• For number constants, the built-in functions such as int() and float() can convert them to integer or float, respectively

• Integer divisions are float in Python 3 (earlier versions had it differently)

• round() converts a float to the nearest integer

• round() takes the optional second parameter to specify desired numbers after decimal point

Page 16: String Conversion

• int() and float() can be used to convert strings

  • The int() function converts a string to an integer

  • The float() function converts a string to a floating-point number

• Conversion only happens if the given string is a number

  • If the string is not a number, an error will occur

Page 17

• User input in Python

  • Using the input() function

  • Example: age = input("Enter your age: ")

• Output

  • Example: Enter your age: 50

  • Type of age variable is a string

Page 18: User Input Conversion

• User inputs are strings

• To convert, we can use int() or eval() or float() commands

• eval() determines int or float type automatically

Example:

• User input: age_ = input("Enter your age: ")

• Output: Enter your age: 50

• Conversion: age = eval(age_)

• Type of age: int

Transcript Notes

Page 19

• Comments

  • To comment, use # before writing

  • Anything after # will be text and not code

• Use:

  • To experiment with the line(s) of code

  • To document what a line of code is doing

  • To describe to other members

Page 20

• Thank you vatsal.maru@utdallas.edu JSOM 4.414