In Python most of the lines you will write will be expressions. Expressions are made of operators and operands. An expression is like 2 + 3 .
Operators are the symbols which tells the Python interpreter to do some mathematical or logical operation. Few basic examples of mathematical operators are given below:
>>> 2 + 3 5 >>> 23 - 3 20 >>> 22.0 / 12 1.8333333333333333
To get floating result you need to the division using any of operand as floating number. To do modulo operation use % operator
>>> 14 % 3 2
The code
#!/usr/bin/env python3
days = int(input("Enter days: "))
months = days / 30
days = days % 30
print("Months = %d Days = %d" % (months, days))
The output
$ ./integer.py Enter days: 265 Months = 8 Days = 25
In the first line I am taking the input of days, then getting the months and days and at last printing them. You can do it in a easy way
#!/usr/bin/env python3
days = int(input("Enter days: "))
print("Months = %d Days = %d" % (divmod(days, 30)))
The divmod(num1, num2) function returns two values , first is the division of num1 and num2 and in second the modulo of num1 and num2.
You can use the following operators as relational operators
| Operator | Meaning |
| < | Is less than |
| <= | Is less than or equal to |
| > | Is greater than |
| >= | Is greater than or equal to |
| == | Is equal to |
| != | Is not equal to |
Some examples
>>> 1 < 2 True >>> 3 > 34 False >>> 23 == 45 False >>> 34 != 323 True
// operator gives the floor division result
>>> 4.0 // 3 1.0 >>> 4.0 / 3 1.3333333333333333
To do logical AND , OR we use and ,*or* keywords. x and y returns False if x is False else it returns evaluation of y. If x is True, it returns True.
>>> 1 and 4 4 >>> 1 or 4 1 >>> -1 or 4 -1 >>> 0 or 4 4
x op = expression is the syntax for shorthand operators. It will be evaluated like x = x op expression , Few examples are
>>> a = 12 >>> a += 13 >>> a 25 >>> a /= 3 >>> a 8.333333333333334 >>> a += (26 * 32) >>> a 840.3333333333334
shorthand.py example
#!/usr/bin/env python3
N = 100
a = 2
while a < N:
print("%d" % a)
a *= aThe output
$ ./shorthand.py 2 4 16
Generally while writing expressions we put spaces before and after every operator so that the code becomes clearer to read, like
a = 234 * (45 - 56.0 / 34)
One example code used to show expressions
#!/usr/bin/env python3
a = 9
b = 12
c = 3
x = a - b / 3 + c * 2 - 1
y = a - b / (3 + c) * (2 - 1)
z = a - (b / (3 + c) * 2) - 1
print("X = ", x)
print("Y = ", y)
print("Z = ", z)
The output
$ ./evaluationexp.py X = 10 Y = 7 Z = 4
At first x is being calculated. The steps are like this
9 - 12 / 3 + 3 * 2 -1 9 - 4 + 3 * 2 - 1 9 - 4 + 6 - 1 5 + 6 - 1 11 - 1 10
Now for y and z we have parentheses, so the expressions evaluated in different way. Do the calculation yourself to check them.
We have to do the type conversions manually. Like
float(string) -> float value int(string) -> integer value str(integer) or str(float) -> string representation >>> a = 8.126768 >>> str(a) '8.126768'
This is a program to evaluate 1/x+1/(x+1)+1/(x+2)+ ... +1/n series upto n, in our case x = 1 and n =10
#!/usr/bin/env python3
sum = 0.0
for i in range(1, 11):
sum += 1.0 / i
print("%2d %6.4f" % (i , sum))The output
$ ./evaluateequ.py 1 1.0000 2 1.5000 3 1.8333 4 2.0833 5 2.2833 6 2.4500 7 2.5929 8 2.7179 9 2.8290 10 2.9290
In the line sum += 1.0 / i what is actually happening is sum = sum + 1.0 / i.
This is a program to evaluate the quadratic equation
#!/usr/bin/env python3
import math
a = int(input("Enter value of a: "))
b = int(input("Enter value of b: "))
c = int(input("Enter value of c: "))
d = b * b - 4 * a * c
if d < 0:
print("ROOTS are imaginary")
else:
root1 = (-b + math.sqrt(d)) / (2.0 * a)
root2 = (-b - math.sqrt(d)) / (2.0 * a)
print("Root 1 = ", root1)
print("Root 2 = ", root2)
In this example we are going to calculate the salary of a camera salesman. His basic salary is 1500, for every camera he will sell he will get 200 and the commission on the month's sale is 2 %. The input will be number of cameras sold and total price of the cameras.
#!/usr/bin/env python3
basic_salary = 1500
bonus_rate = 200
commision_rate = 0.02
numberofcamera = int(input("Enter the number of inputs sold: "))
price = float(input("Enter the total prices: "))
bonus = (bonus_rate * numberofcamera)
commision = (commision_rate * numberofcamera * price)
print("Bonus = %6.2f" % bonus)
print("Commision = %6.2f" % commision)
print("Gross salary = %6.2f" % (basic_salary + bonus + commision))
The output
$ ./salesmansalary.py Enter the number of inputs sold: 5 Enter the total prices: 20450 Bonus = 1000.00 Commision = 2045.00 Gross salary = 4545.00