SyntaxError: print doesn't work in eval()

Question

Code:

eval("print('foobar')")

Output:

Traceback (most recent call last):
  File "Untitled.py", line 30, in <module>
    eval("print('foobar')")
  File "<string>", line 1
    print('foobar')
        ^
SyntaxError: invalid syntax

What am I doing wrong?

Given that it throws a `SyntaxError` it's python-2.x. You need `exec` for statements like `print` in python 2. — MSeifert, May 28 '17 at 10:57
w.r.t. the duplicate: I'm voting to leave this open. The potential duplicate does not mention `print` specifically, so in terms of internet search queries leaving the current question open would help. — kfx, May 28 '17 at 12:02

score 2 · Answer 1 · answered May 28 '17 at 10:53

2

print is an operator in Python 2, and a function in Python 3. Which version do you use?

answered May 28 '17 at 10:53

^ This is essentially the correct answer. `eval` works on expressions only. In Python 3, `print` is a function, and so its use is a valid expression. In Python 2, its use is a statement, not an expression, so it won't evaluate. See https://stackoverflow.com/questions/22558548/eval-syntaxerror-invalid-syntax-in-python for more info – daveruinseverything May 28 '17 at 10:55
If you remove the "which version do you use" part and say that's the reason why it fails on python-2.x it would be an even better answer. – MSeifert May 28 '17 at 10:59
Using Python 2 so I want exec() then? Makes a lot of sense, thanks – Ibraheem Rodrigues May 28 '17 at 11:00
@IbraheemRodrigues You don't want to use `exec` or `eval` - trust me! But if you have to use them, then you need `exec` for `print` in python 2. – MSeifert May 28 '17 at 11:01
2

I would use "statement" instead of "operator". https://docs.python.org/2/reference/simple_stmts.html#print – mzjn May 28 '17 at 11:02
@MSeifert In terms of security (code injection)? I am using it to make a [brainfuck](https://en.wikipedia.org/wiki/Brainfuck) interpreter. – Ibraheem Rodrigues May 28 '17 at 15:13

score 2 · Accepted Answer · answered May 28 '17 at 10:57

2

You have to use the exec function. Like this:

exec("print('foobar')")

See What is the difference between an expression and a statement in Python? for more informations.

answered May 28 '17 at 10:57

Zcode

425
3
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score 2 · Answer 3 · answered May 28 '17 at 11:27

eval evaluates expressions, not statements, so you need to pass it the print function, not the print statement. By default, print is a statement in Python 2, and the print statement doesn't exist in Python 3. However, the print function is available in recent versions of Python 2 via a __future__ import. The print function is actually defined in those versions of Python 2 but it's masked by the print statement; the import makes the print statement unavailable, thus exposing the print function.

Demo, tested on Python 2.6.6:

from __future__ import print_function

eval("print('foobar')")

output

foobar

BTW, it's generally not a good idea to use eval or exec, unless you have no alternative. They are relatively slow, and have security risks if you pass them unsanitized strings to evaluate / execute. For details, please see Eval really is dangerous by SO veteran Ned Batchelder. To evaluate simple Python literals you can use ast.literal_eval.

SyntaxError: print doesn't work in eval()

3 Answers3