Download Math and Data Types

Math, Data
Types
Python Math Operations
Operation
Operator
Addition
+
Subtraction
–
Multiplication
*
Division (floating point)
/
Division (integer)
//
Expressions
 We use operators along with numeric data to create “math
expressions” that Python can evaluate on our behalf
 However, unless you ask python to output the value of the
expression, it will not do so
 Example:
- writing “5 + 2” in python will not output anything, although the
calculation will be done
- instead, you must write something like:
print (5 + 2 + 9 + 3)
>> 19
Storing results of an expression
 You can also store the result of your expression into a
variable
 Example:
answer = 5 + 2
print ( ‘the answer to 5 + 2 is‘, answer )
>> the answer to 5 + 2 is 7
Using variables in math expressions
 Math expressions don’t need to be done on only
numeric literals
 Example:
price = 100.00
sales_tax = 0.07
total = price + price * sales_tax
Data Types
 Python needs to know how to set aside memory in your
computer based on what kind of information you want
to store
 There are three basic types of data types that we will be
working with:
 Strings (character-based data)
 Number (floats/integers)
 Boolean variables (True/False)
Numeric Data Types
 Integers:
 Whole numbers that do not contain a decimal point
 Abbreviated as “int” in Python
 Example: 5 , - 5 , 100 , 100023
 Floating Point Numbers:
 Numbers that contain a decimal point
 Abbreviated as “float” in Python
 Example: 5.0 , - 5.0 , 100.99 , 0.232415
Strictly Typed Languages
 Python is not a strictly typed language, which means
that you don’t need to pre-declare what kind of data
your variables will be holding, it will automatically assign
it for you
Loosely Typed
Strictly Typed
Python
C
PHP
C++
JavaScript
Java
Perl
ActionScript
Strictly Typed Languages
ActionScript
Java
var name:String = “Donald”;
string name = “Donald” ;
var top_speed:Number = 50;
int top_speed = 50 ;
var gravity:Number = 9.5;
float gravity = 9.5 ;
Numeric Data Types
 You can store numeric data inside variables and Python
will automatically assign it a type according to how it is
created
 num_1 = 5
# Python recognizes this as an int
 num_2 = 4.99
# Python recognizes this a float
 Keep in mind that you can not use separators or symbols
when storing numeric data
 num_3 = $ 5 , 122.39
# This will cause an error!
Practice
5
 5.5
 “Hello”
 “5.5”
 2.975
 2.0
 “$2.99”
Practice
5
# int
 5.5
# float
 “Hello”
# string
 “5.5”
# string
 2.975
# float
 2.0
#float
 “$2.99”
# string
Input and Math expressions
Recall that the input function always
returns a string
average = input (“what was the average?”)
what was the average? 53
# this will be
inputted into
the variable as
a string, “53”
Input and Math expressions
average = input (“what was the average?”)
new_average = average + 2
# this will cause an error because you are trying to
add a string to some numeric data
So, how can we convert our inputted data into
a numeric data type that Python supports?
(an integer, or a float)
Concatenation
We are able to use math operators on more
than numeric data types. We can “add” and
also “multiply” strings.
When we add two strings together, we call this
concatenation.
Example:
print(“53” + “2”)
>> 532
Concatenation
This will help us with a problem we ran into
previously.
Remember that our print function by nature will
add a space between arguments, whenever it
recognizes a comma.
print (“Average Scores for \“”, class, “\“”)
>> Average Scores for “ Intro to Programming ”
Concatenation
Now, with the “+” operator, we can literally
attach two strings together without any
additional spaces.
print (“Average Scores for \“” + class + “\“”)
>> Average Scores for “Intro to Programming”
String Repetition
A similar function is applied when we “multiply”
strings with a numeric data type.
The * operator will print out a string the number
of times it is being “multiplied by” but in a literal
sense.
print (“Hello” * 3)
>> HelloHelloHello
If we do not convert data types …
# ask user for monthly salary
monthly_salary = input (‘how much do you make a month?’)
# calculate annual salary
annual_salary = monthly_salary * 12
# print result
print ( ‘that means you make’, annual_salary, ‘in a year’)
>> how much do you make a month? 100
that means you make 100100100100100100100100100100100100 in a year
The float( ) and int ( ) functions
The float ( ) and int ( ) functions are data type
conversion functions.
They take the passed argument and convert
that into a specific data type
The float( ) and int ( ) functions
# ask user for monthly salary
monthly_salary = input (‘how much do you make a month?’)
# convert salary into float
monthly_salary_float = float(monthly_salary)
# calculate annual salary
annual_salary = monthly_salary_float * 12
# print result
print ( ‘that means you make’, annual_salary, ‘in a year’)
Nesting data type conversions
 It took us two steps to convert our data, but we can do it
in one!
 We use a technique called “nesting”
 Example:
my_num = float ( input ( ‘give me a number!’ ) )
Nesting data type conversions
Practice
Ask the user for two numbers. You can assume they
will input floating point numbers.
Compute the following and print it out to the user:
 The sum of the numbers
 The difference between the numbers
 The product of the numbers
 The quotient of the first number divided by the second