Preparing a variable value for display using %d in Python

Question

GOAL:

I'm trying to display (assumed float) value as a decimal, within a print call using the '%d' operator.

PROBLEM

Documentation states that '%d' can only take the value of a decimal. Taking this into account, I imported the 'decimal' module and attempted to convert using the decimal function. The result was not altered, and my code would return what looks like a 'floored' price for my oranges (my oranges are not happy with that). What am I doing wrong?

CODE

 import decimal

    prices = {
        "banana":4,
        "apple":2,
        "orange":1.5,
        "pear":3
        }

    stock = {
        "banana":6,
        "apple":0,
        "orange":32,
        "pear":15
        }

    for x in prices:
        print x
        print "price: %d" % (decimal.Decimal(prices[x]))

        for y in stock:
            if y == x:
                print "stock: %d" % (stock[y])

RESULT

orange
price: 1 // Need this to return the price (1.5)
stock: 32
pear
price: 3
stock: 15
banana
price: 4
stock: 6
apple
price: 2
stock: 0

Krzysztof Kosiński · Accepted Answer · 2013-10-15 00:26:14Z

1

If you want to print floating point numbers, use the %f specifier. For example, this will print the price with 2 decimal digits of precision:

print "price: %.2f" % prices[x]

See here for more documentation: http://docs.python.org/2/library/stdtypes.html#string-formatting

answered Oct 15, 2013 at 0:26

Krzysztof Kosiński

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5 Comments

brooklynsweb Over a year ago

Thanks for the answer @Krzysztof Kosiński; should have made a point to check how many specifier types Python provides before trying to hack things. But regarding my code; I converted my value to a decimal, why did it not display a decimal version of my value?

wwii Over a year ago

If you look at the documentation link that Krzysztof Kosiński posted you can see that the 'd' format is a signed integer decimal format.

brooklynsweb Over a year ago

Based on the doc, if anything with a decimal point is considered a float, then how would you represent a 'decimal' (signed integer decimal)?' I ask because the 'd' specifier expects that, but apparently my price for oranges was a float.

DSM Over a year ago

@brooklynsweb: ah, I think I see what's confusing you. The word "decimal" here doesn't mean "decimal" as opposed to "integer", it means "decimal" as opposed to "hexadecimal", i.e. base 10. %d specified a signed integer in base 10.

bgporter Over a year ago

The docs here use the word 'decimal' in its definition of "a number in a base 10 representation", not as "a number that's got a decimal point in its representation" or "an instance of the Python decimal.Decimal class". Compare to e.g. the %x format specifier that displays as hexadecimal.

aIKid · Accepted Answer · 2013-10-15 00:56:20Z

0

Well, here's my attempt.

The %d specifier converts the number to an integer of base 10. So when you do something like:

print "price: %d"%Decimal("1.5")

It would print price:1.

To achieve what you want, you can use the %f specifier:

print "price: %.2f"%Decimal("1.5")

See more on formatting here. Hope this helps!

answered Oct 15, 2013 at 0:56

aIKid

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