Reputation: 4801

"+=" causing SyntaxError in Python

n = 1
p = 4
print n += p

gives me:

File "p7.py", line 17

print n += p

SyntaxError: invalid syntax

How can this problem be fixed?

Upvotes: 3

Answers (6)

orlp

Reputation: 117691

n += p is equal to n = n + p. This is a statement on its own and cannot be printed out. You probably meant print n + p.

EDIT:

figured it out... somewhat. taking out the print statement makes it work. I dont understand the rule here, why it breaks with print, but Ill keep looking

I would seriously suggest to get a book about Python and learn from that. You obviously (not meant as an insult, just informing you) have no idea what you are doing.

Upvotes: 4

Tim Pietzcker

Reputation: 336158

n += p is a statement in Python, not an expression that returns a value you could print. This is different from a couple of other languages, for example Ruby, where everything is an expression.

You need to do

n += p
print n

Upvotes: 24

user395760

Reputation:

Assignment, including "augmented" assignment (x op= expr as shorcut for x = x op expr), is a statement, not an expression. So it doesn't result in a value. You can't print the result of something that doesn't result in anything - but that's what you're telling Python to do: "Evaluate n += p, then print the result of that."

If you want to modify n and print the new n, do that on two lines. If you just want to print the sum of n and p without modifying either, use + instead of +=.

Upvotes: 7