Weird program behaviour in Python

Question

When running the following code, which is an easy problem, the Python interpreter works weirdly:

n = input()
for i in range(n):
    testcase = raw_input()
    #print i
    print testcase[2:(int(testcase[0])+1)]+testcase[(int(testcase[0])+2):]

The problem consists in taking n strings and deleting a single character from them. For example, given the string "4 PYTHON", the program should output "PYTON". The code runs ok, but if I take out the comment mark, the statement print i makes the interpreter give an unexpected EOF while parsing. Any idea on why this happens?

EDIT: I'm working under Python 2.5, 32 bits in Windows.

Which version of python? The for loop works fine for me with 'print i' uncommented on windows python 2.6.2c1 — workmad3
– workmad3, Commented Jun 11, 2009 at 19:10

M.J. · Accepted Answer · 2009-06-11 19:18:25Z

4

Are you sure that the problem is the print i statement? The code works as expected when I uncomment that statement and run it. However, if I forget to enter a value for the first input() call, and just enter "4 PYTHON" right off the bat, then I get:

"SyntaxError: unexpected EOF while parsing"

This happens because input() is not simply storing the text you enter, but also running eval() on it. And "4 PYTHON" isn't valid python code.

answered Jun 11, 2009 at 19:18

M.J.

1,4661 gold badge9 silver badges3 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Fernando Martin Over a year ago

I know, "4 PYTHON" was just an example of the way strings are formatted. The interpreter gives me an EOF even if I assign a value for n.

Nicolas Dumazet Over a year ago

you need raw_input; not input(). Input() expects a valid Python expression. read docs.python.org/library/functions.html#input

John Y · Accepted Answer · 2009-06-13 03:28:35Z

1

I am yet another who has no trouble with or without the commented print statement. The input function on the first line is no problem as long as I give it something Python can evaluate. So the most likely explanation is that when you are getting that error, you have typed something that isn't a valid Python expression.

Do you always get that error? Can you post a transcript of your interactive session, complete with stack trace?

answered Jun 13, 2009 at 3:28

John Y

14.6k2 gold badges51 silver badges76 bronze badges

1 Comment

Fernando Martin Over a year ago

"complete with stack trace?" This was it; when the first value was typed in it was fetched by another input() in the stack.

nik · Accepted Answer · 2009-06-11 19:28:21Z

1

This worked for me too, give it a try...

n = raw_input()
n = int(n)
for i in range(n):
  testcase = raw_input()
  print i
  print testcase[2:(int(testcase[0])+1)]+testcase[(int(testcase[0])+2):]

Note the n = int(n)

PS: You can continue to use n = input() on the first line; i prefer raw_input.

edited Jun 11, 2009 at 19:28

answered Jun 11, 2009 at 19:22

nik

13.5k3 gold badges43 silver badges58 bronze badges

1 Comment

Fernando Martin Over a year ago

This works, but I still don't get why it doesn't when using input().

Collectives™ on Stack Overflow

Weird program behaviour in Python

3 Answers 3

2 Comments

1 Comment

1 Comment

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

1 Comment

1 Comment

Related