Floating Point in Python

Question

I'm learning via Learn Python The Hard Way and I've come across:

Notice the math seems “wrong”? There are no fractions, only whole numbers. Find out why by researching what a “floating point” number is.

I've read what it is on: http://docs.python.org/tutorial/floatingpoint.html

I can't figure out on how I can output floating point numbers, I've thought about using round(3 + 3, 2).

Is this right?

Solution 1

For floating point numbers you write a period after the number, and a zero (if it's a whole number).

Like this:

1.0 <---- Floating point.

1 <------- integer

That is how python interprets them.

if my_answer != your_question:
    print "I did not understand your question. Please rephrase it."
else:
    print "Good luck. Python is fun."

---

I agree with rohit, the 0 is not needed. Although it makes things easier for beginners.

Solution 2

Passing a value to the float() constructor will make it a float if possible.

print float(2)
print float('4.5')

Use string interpolation or formatting to display them.

print '%.3f' % 4.53

Solution 3

3 is an integer.

3.0 is a float.

>>> type(3)
<type 'int'>
>>> type(3.0)
<type 'float'>

round():

Round a number to a given precision in decimal digits (default 0 digits). This always returns a floating point number.

So that is why in your case, 6.0 is returned.

Solution 4

Orange, read the last question in the lesson, the author gave you the answer

Why does / (divide) round down? It's not really rounding down; it's just dropping the fractional part after the decimal. Try doing 7.0 / 4.0 and compare it to 7 / 4 and you'll see the difference.

good luck

Solution 5

Agree with all of the answers above. You don't even need to put a zero after the period though.

For example:

In [1]: type(3)
Out[1]: <type 'int'>

In [2]: type(3.)
Out[2]: <type 'float'>

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Comments

[Drewdin]

I'm doing this example right now, this answered my question, thanks!

[R891]

Python 2 will give you 7. Python 3 will give you 6.75. Try 7 / 2 in both version of Python to see the difference.