stoneskin

learning coding with Scratch , Python and Java

Session 1.2 Basic Python -1: Variables and Types

2.1 Number and String

1,2,3.. is number

print(1) will print 1

"I am learn Python" is a string

print ("Hi") will print a string in output.

2.1.1 Let Python do math for you

Math is the basic function of the Python, please try below code and learn the basic operation of “+,-,*, /, %”

x = 3
y = 4
answerPlus = x+y
answerMinus = x-y
answerMultiple = x*y
answerDivide = x/y
answerWhatEver = (x*y)+(x-y)/x
answerMode=x%y

print(x)    #3
print(y)    #4
print(answerPlus)       #7
print(answerMinus)      #-1
print(answerMultiple)   #12
print(answerDivide)     #0.75
print(answerWhatEver)   #11.666666666666666
print(answerMode)       #3

2.1.2 Assign a Number to a Variable and print it

Use print() function you could print the result, but python can’t print mix the data type of number and a string.

Below is working

x = 3
print(x)

But this is not working:

print("x="+x)

You will got error like below: typeerror

To correct the type error, you need convert the number to string first.

print("x=" + str(x))

2.1.3 More Assignment example

Assign a expression to a variable

x = 3
y= x+2

example of chain assignment

a = b = x*(y+x)

Check the results:

print("a="+ str(a))
print("b="+ str(b))

please try yourself and print the result.

2.1.4 Math Operators in Python

There are more math operators you may need, pleas try them and see how it works. math operators

2.1.5 practices

2.2 Type

2.2.1 Type of number: Int and float

All variable has a type in python, for example, the string “abc” has a type “String”.

The number 1,2,3 is integer number, but 1.23 is fraction number. In python, the integer number type is int the fraction number type is float

You could use type(variable) to get the type of the variable

number = 9
print (type(number))

float_number = 9.0
print(type(float_number))

you will got below type nt

2.2.2 Convert the number type

The type of number could convert each other:

number = 9
f_number= float(number)

print(number)
print(f_fumber)

please run it ans see the result yourself.

3.2.3 Augmented Assignment

Augmented assignment is the combination, in a single statement, of a binary operation and an assignment statement:

augmented

Try below code to see the result

number = 9.0
print("number = " + str(number))

number -= 2
print("number = " + str(number))

number += 5
print("number = " + str(number))

2.3 Boolean Type and Operators

2.3.1 Boolean Type

The Boolean Type only have two value: true and false

You could compare two value and see the result:

a = 2
b = 3
c = 2
result1 = (a == b)
print(result1)      # false
result2 = (a == c)  # true
print(result2)      # true

2.3.2 Comparison Operator

There is more operation will got boolean result: comparasion

2.3.3 Logic Operators

Logic operators are used to combine the two boolean statements:

Operator Description Example
and Return true if both are true x<4 and x>1
or Return True if one of the value is true x<4 or x>10
not reverse the result not(x>y)

2.4 Practice