eval函数在Python 2.7中无法正常工作

Question

As far as I know the eval function lets a python program run python code within itself.

I want to run a print() command using eval function in Python2.7 , but I received the following error :

>>> print "test"
test
>>> command='print "test"'
>>> command
'print "test"'
>>> eval(command)

Traceback (most recent call last):
  File "<pyshell#11>", line 1, in <module>
    eval(command)
  File "<string>", line 1
    print "test"
        ^
SyntaxError: invalid syntax
>>> 

Note that I don't have any problem with this command it python3.4 :

>>> print ("test")
test
>>> command='print("test")'
>>> command
'print("test")'
>>> eval(command)
test
>>> 

Answer 1

In Python 2 print xxx is a statement, not an expression. eval is for evaluating expressions; you can use exec for executing statements.

In Python 3, print(xxx) is a function call, so it can be evaluated.