float ¶

A number with a decimal part is called a float .

In [4]:

print(type(3.14))

print(type(3.14))

<class 'float'>

We can also do negative numbers

In [5]:

print(type(-0.5))

print(type(-0.5))

<class 'float'>

or whole numbers with but with a .0 at the end.

In [6]:

print(type(2.0))

print(type(2.0))

<class 'float'>

Remember, Python stores int data differently than float . So if you put a number and there is a . anywhere, it will store it as a float . This . with a number is an instruction to Python to store it as a float .

In [7]:

print(type(2.))

print(type(2.))

<class 'float'>

Even though there is no 0 after the . , Python stores it as a float .

I can do arithmetic as well.

In [8]:

result = 5.0 + 5.0
print(result)
print(type(result))

result = 5.0 + 5.0 print(result) print(type(result))

10.0
<class 'float'>

Note that answer is still 10 , but now it is a float because my expression 5.0 + 5.0 uses float and not int .

Okay, but what if I do this.

In [9]:

result = 5 / 5

result = 5 / 5

What would the type be? Well, let's find out.

In [10]:

print(type(result))

print(type(result))

<class 'float'>

It is a float , why? Well, the answer is that Python, and all programming languages, aim to be consistent and minimize surprizes. If we were to perform the following division

In [11]:

result = 3.14159 / 52.910
print(result)
print(type(result))

result = 3.14159 / 52.910 print(result) print(type(result))

0.059376110376110375
<class 'float'>

It is no surprise that this would be a float . However, what if we mixed data types?

In [12]:

result = 3 / 52.910

result = 3 / 52.910

Which data type should Python use?

In [13]:

print(result)
print(type(result))

print(result) print(type(result))

0.056700056700056706
<class 'float'>

It is float ! If we rounded 0.059376110376110375 to be an int , this would be 0 , which we know it is not correct. Thus, Python always errs on the side of caution and "upgrades" int values to float whenever there could be an issue—even if the result could technically be an int like in our 5 / 5 example.