Obtain function from string in python

Question

Is it possible to define a function to behave as follows?

text = "def x(a):\treturn a+1"
f = ??(text)
f(1)
>> 2

• jonrsharpe: @BhargavRao I think that's the question...
• ForceBru: Just exec("print 'hello'") or any other
• Kevin: Why would you want to do this? If the reasoning is "because I want to define a function on the same line that I use it, and def can't be on the same line as other statements", then you can instead use lambdas: print (lambda a: a+1)(1)
• jamborta: @Kevin I am creating an API where the user can define functions that would be executed by other function (which are actually lambdas).

Answer 1

You can use exec()

text = "def x(a):\treturn a+1"
exec(text)
print x(5) # gives 6

• Kevin: Now the hard part is, getting f(5) to give 6, when you don't know the contents of text and don't know that the function is currently called x, and so you can't just do f = x

Answer 2

text = "lambda a: a + 1"
f = eval(text)
f(1) # 2

• Hugh Bothwell: @bhargavrao: any method of running arbitrary code is dangerous.
• Hugh Bothwell: @forcebru: yes, that's why I converted it to a lambda!

Answer 3

here is another solution:

text = "def x(a):\treturn a+1"
f = {}
exec text in f
f['x'](1)
>> 2

• CodeMouse92: Please add some explanation. Imparting the underlying logic is more important than just giving the code, because it helps the OP and other readers fix this and similar issues themselves.