python syntax error 30/09/2013

Question

My code is returning an error on the line where it says "<= 80" on the = part. Why is that? How can I fix it?

#Procedure to find number of books required
def number_books():
    number_books = int(raw_input("Enter number of books you want to order: "))
    price = float(15.99)
    running_total = number_books * price
    return number_books,price

#Procedure to work out discount
def discount(number_books):
    if number_books >= 51 and <= 80:
        discount = running_total / 100 * 10
    elif number_books >= 11 and <=50:
        discount = running_total / 100 * 7.5
    elif number_books >= 6 and <=10:
        discount = running_total / 100 * 5
    elif number_books >=1 and <=5:
        discount = running_total / 100 * 1
    else print "Max number of books available to order is 80. Please re enter number: "        
        return discount

#Calculating final price
def calculation(running_total,discount):
    final_price = running_total - discount

#Display results
def display(final_price)
print "Your order of", number_books, "copies of Computing science for beginners will cost £", final_price 

#Main program
number_books()
discount(number_books)
calculation(running_total,discount)
display(final_price)

any help would be greatly appreciated

@thegrinner: The syntax is quite obviously wrong, and a common beginners mistake. — Martijn Pieters, Sep 30 '13 at 17:53
@MartijnPieters I know, I just want to get the OP in the habit of posting the full error so it won't slow things down if they have more questions in the future. — thegrinner, Sep 30 '13 at 17:54

karthikr · Answer 1 · 2013-09-30T17:57:49.873

This is invalid:

if number_books >= 51 and <= 80

Try:

if number_books >= 51 and number_books <= 80

The same with all the other occurances thereof

Or, as nneonneo mentions,

if 51 <= number_books <= 80

Also, you need to return discount the right way at the end (That would be another issue you would encounter once this issue is resolved).

So,

def discount(number_books):

    if 51 <= number_books <= 80:
        discount = running_total / 100 * 10
    elif 11 <= number_books <= 50: 
        discount = running_total / 100 * 7.5
    elif 6 <= number_books <= 10: 
        discount = running_total / 100 * 5
    elif 1 <= number_books <= 5:
        discount = running_total / 100 * 1

    return discount


def number_books():
    num_books = int(raw_input("Enter number of books you want to order: "))
    if numb_books <= 0 or num_books > 80:
        print "Max number of books available to order is 80, and minimum is 1. Please re enter number: "        
        number_books()

    price = float(15.99)
    running_total = num_books * price
    return number_books,price

Better yet, `if 51 <= number_books <= 80` – nneonneo Sep 30 '13 at 17:52 — nneonneo, Sep 30 '13 at 17:52

nneonneo · Answer 2 · 2013-09-30T17:58:15.283

6

If you're doing range testing, you can use a chained comparison:

if 51 <= number_books <= 80:

As to why you get a syntax error: both sides of an and (or or) operator must be full expressions. Since <= 80 is not a complete expression, you get a syntax error. You'd need to write number_books >= 51 and number_books <= 80 to fix that syntax error.

edited Sep 30 '13 at 17:58

answered Sep 30 '13 at 17:52

nneonneo

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You might want to link to the documentation here; this feature is called 'chained comparisons'. You did not explain where the OP went wrong in their understanding, however. – Martijn Pieters Sep 30 '13 at 17:54
Thanks, added a documentation link. – nneonneo Sep 30 '13 at 17:55
Explain a bit more why he is getting the error, because IMO, this currently isn't a proper answer to his question/doubt. – KurzedMetal Sep 30 '13 at 17:56
@KurzedMetal: was working on that edit even as you commented :) Thanks. – nneonneo Sep 30 '13 at 17:58

python syntax error 30/09/2013

2 Answers2