PYTHON SYNTAX _13/14

ValueError

Python automatically assigns a variable the appropriate datatype based on the value it is given. A variable with the value 7 is an integer, 7. is a float, "7" is a string. Sometimes we will want to convert variables to different datatypes. For example, if we wanted to print out an integer as part of a string, we would want to convert that integer to a string first. We can do that using str():

age = 13
print "I am " + str(age) + " years old!"

This would print:

>>> "I am 13 years old!"

Similarly, if we have a string like "7" and we want to perform arithmetic operations on it, we must convert it to a numeric datatype. We can do this using int():

number1 = "100"
number2 = "10"

string_addition = number1 + number2 
#string_addition now has a value of "10010"

int_addition = int(number1) + int(number2)
#int_addition has a value of 110

If you use int() on a floating point number, it will round the number down. To preserve the decimal, you can use float():

string_num = "7.5"
print int(string_num)
print float(string_num)

>>> 7
>>> 7.5

Exercise

1.

Create a variable called product that contains the result of multiplying the float value of float_1 and float_2.

2.

Create a string called big_string that says:

The product was X

with the value of product where the X is.

Hint! You can combine strings by casting the numerical value to a string and using the + operator:

"I have " + str(18) + " dogs at home!"

SOL.