Why does input() give a SyntaxError when I just press enter?

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For Python 2, you want raw_input, not input. The former will read a line. The latter will read a line and try to execute it, not advisable if you don’t want your code being corrupted by the person entering data.

For example, they could do something like call arbitrary functions, as per the following example:

def sety99():
    global y
    y = 99

y = 0
input ("Enter something: ")
print y

If you run that code under Python 2 and enter sety99(), the output will 99, despite the fact that at no point does your code (in its normal execution flow) purposefully set y to anything other than zero (it does in the function but that function is never explicitly called by your code). The reason for this is that the input(prompt) call is equivalent to eval(raw_input(prompt)).

See here for the gory details.

Keep in mind that Python 3 fixes this. The input function there behaves as you would expect.

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