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Is there something like a reverse eval() function?

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1

Imagine the following problem: you have a dictionary of some content in python and want to generate python code that would create this dict. (which is like eval but in reverse)
Is there something that can do this?

Scenario:
I am working with a remote python interpreter. I can give source files to it but no input. So I am now looking for a way to encode my input data into a python source file.

Example:

d = 'a': [1,4,7]
str_d = reverse_eval(d)
# "'a': [1, 4, 7]"
eval(str_d) == d

python eval

share|improve this question

edited May 29 at 6:26

Christian

asked Mar 25 at 10:07

ChristianChristian

37711 gold badge66 silver badges1919 bronze badges

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Can you be more specific by providing an example?
  
  – Vasilis G.
  Mar 25 at 10:11
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  rather reverse ast.literal_eval then.
  
  – Jean-François Fabre♦
  Mar 25 at 10:20
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Not quite sure why you are trying to do this. It might be an XY problem for which pickle is the solution for the unasked X problem.
  
  – John Coleman
  Mar 25 at 10:20
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @JohnColeman Let's not casually throw around pickle, please. We're giving newbies the impression that pickle can solve their problem, without mentioning that it opens up their program to an arbitrary code execution vulnerability. That's how we end up with people sending pickled data over an unsecured socket connection.
  
  – Aran-Fey
  Mar 25 at 10:25
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Aran-Fey Good point -- but of course eval has the same problems. Fortunately, the pickle documentation that I linked to has a very clear warning which is formatted so that it is the first thing you see when you look at it.
  
  – John Coleman
  Mar 25 at 10:28
  
  

  
  
  
  

 | 
show 1 more comment

1

Imagine the following problem: you have a dictionary of some content in python and want to generate python code that would create this dict. (which is like eval but in reverse)
Is there something that can do this?

Scenario:
I am working with a remote python interpreter. I can give source files to it but no input. So I am now looking for a way to encode my input data into a python source file.

Example:

d = 'a': [1,4,7]
str_d = reverse_eval(d)
# "'a': [1, 4, 7]"
eval(str_d) == d

python eval

share|improve this question

edited May 29 at 6:26

Christian

asked Mar 25 at 10:07

ChristianChristian

37711 gold badge66 silver badges1919 bronze badges

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Can you be more specific by providing an example?
  
  – Vasilis G.
  Mar 25 at 10:11
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  rather reverse ast.literal_eval then.
  
  – Jean-François Fabre♦
  Mar 25 at 10:20
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Not quite sure why you are trying to do this. It might be an XY problem for which pickle is the solution for the unasked X problem.
  
  – John Coleman
  Mar 25 at 10:20
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @JohnColeman Let's not casually throw around pickle, please. We're giving newbies the impression that pickle can solve their problem, without mentioning that it opens up their program to an arbitrary code execution vulnerability. That's how we end up with people sending pickled data over an unsecured socket connection.
  
  – Aran-Fey
  Mar 25 at 10:25
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Aran-Fey Good point -- but of course eval has the same problems. Fortunately, the pickle documentation that I linked to has a very clear warning which is formatted so that it is the first thing you see when you look at it.
  
  – John Coleman
  Mar 25 at 10:28
  
  

  
  
  
  

 | 
show 1 more comment

Imagine the following problem: you have a dictionary of some content in python and want to generate python code that would create this dict. (which is like eval but in reverse)
Is there something that can do this?

Scenario:
I am working with a remote python interpreter. I can give source files to it but no input. So I am now looking for a way to encode my input data into a python source file.

Example:

d = 'a': [1,4,7]
str_d = reverse_eval(d)
# "'a': [1, 4, 7]"
eval(str_d) == d

python eval

share|improve this question

edited May 29 at 6:26

Christian

asked Mar 25 at 10:07

ChristianChristian

37711 gold badge66 silver badges1919 bronze badges

d = 'a': [1,4,7]
str_d = reverse_eval(d)
# "'a': [1, 4, 7]"
eval(str_d) == d

share|improve this question

edited May 29 at 6:26

Christian

asked Mar 25 at 10:07

ChristianChristian

37711 gold badge66 silver badges1919 bronze badges

share|improve this question

edited May 29 at 6:26

Christian

asked Mar 25 at 10:07

ChristianChristian

37711 gold badge66 silver badges1919 bronze badges

asked Mar 25 at 10:07

ChristianChristian

37711 gold badge66 silver badges1919 bronze badges

asked Mar 25 at 10:07

ChristianChristian

37711 gold badge66 silver badges1919 bronze badges

2 Answers
2

active

oldest

votes

7

repr(thing)

will output text that when executed will (in most cases) reproduce the dictionary.

share|improve this answer

answered Mar 25 at 10:12

David JonesDavid Jones

2,2161919 silver badges3232 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  To elaborate: the purpose of repr is to return a string which, if possible, will reconstruct an equivalent object when passed to eval. That's why the Python REPL uses repr when printing objects.
  
  – Daniel Pryden
  Mar 25 at 10:13
  

  
  
  
  

add a comment | 

1

Actually, it's important for which types of data do you want this reverse function to exist. If you're talking about built-in/standard classes, usually their .__repr__() method returns the code you want to access. But if your goal is to save something in a human-readable format, but to use an eval-like function to use this data in python, there is a json library.
It's better to use json for this reason because using eval is not safe.
Json's problem is that it can't save any type of data, it can save only standard objects, but if we're talking about not built-in types of data, you never know, what is at their .__repr__(), so there's no way to use repr-eval with this kind of data

So, there is no reverse function for all types of data, you can use repr-eval for built-in, but for built-in data the json library is better at least because it's safe

share|improve this answer

answered Mar 25 at 10:31

Kolay.NeKolay.Ne

7699 bronze badges

add a comment | 

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7

repr(thing)

will output text that when executed will (in most cases) reproduce the dictionary.

share|improve this answer

answered Mar 25 at 10:12

David JonesDavid Jones

2,2161919 silver badges3232 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  To elaborate: the purpose of repr is to return a string which, if possible, will reconstruct an equivalent object when passed to eval. That's why the Python REPL uses repr when printing objects.
  
  – Daniel Pryden
  Mar 25 at 10:13
  

  
  
  
  

add a comment | 

7

repr(thing)

will output text that when executed will (in most cases) reproduce the dictionary.

share|improve this answer

answered Mar 25 at 10:12

David JonesDavid Jones

2,2161919 silver badges3232 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  To elaborate: the purpose of repr is to return a string which, if possible, will reconstruct an equivalent object when passed to eval. That's why the Python REPL uses repr when printing objects.
  
  – Daniel Pryden
  Mar 25 at 10:13
  

  
  
  
  

add a comment | 

repr(thing)

will output text that when executed will (in most cases) reproduce the dictionary.

share|improve this answer

answered Mar 25 at 10:12

David JonesDavid Jones

2,2161919 silver badges3232 bronze badges

repr(thing)

share|improve this answer

answered Mar 25 at 10:12

David JonesDavid Jones

2,2161919 silver badges3232 bronze badges

answered Mar 25 at 10:12

David JonesDavid Jones

2,2161919 silver badges3232 bronze badges

answered Mar 25 at 10:12

David JonesDavid Jones

2,2161919 silver badges3232 bronze badges

1

Actually, it's important for which types of data do you want this reverse function to exist. If you're talking about built-in/standard classes, usually their .__repr__() method returns the code you want to access. But if your goal is to save something in a human-readable format, but to use an eval-like function to use this data in python, there is a json library.
It's better to use json for this reason because using eval is not safe.
Json's problem is that it can't save any type of data, it can save only standard objects, but if we're talking about not built-in types of data, you never know, what is at their .__repr__(), so there's no way to use repr-eval with this kind of data

So, there is no reverse function for all types of data, you can use repr-eval for built-in, but for built-in data the json library is better at least because it's safe

share|improve this answer

answered Mar 25 at 10:31

Kolay.NeKolay.Ne

7699 bronze badges

add a comment | 

1

Actually, it's important for which types of data do you want this reverse function to exist. If you're talking about built-in/standard classes, usually their .__repr__() method returns the code you want to access. But if your goal is to save something in a human-readable format, but to use an eval-like function to use this data in python, there is a json library.
It's better to use json for this reason because using eval is not safe.
Json's problem is that it can't save any type of data, it can save only standard objects, but if we're talking about not built-in types of data, you never know, what is at their .__repr__(), so there's no way to use repr-eval with this kind of data

So, there is no reverse function for all types of data, you can use repr-eval for built-in, but for built-in data the json library is better at least because it's safe

share|improve this answer

answered Mar 25 at 10:31

Kolay.NeKolay.Ne

7699 bronze badges

add a comment | 

Actually, it's important for which types of data do you want this reverse function to exist. If you're talking about built-in/standard classes, usually their .__repr__() method returns the code you want to access. But if your goal is to save something in a human-readable format, but to use an eval-like function to use this data in python, there is a json library.
It's better to use json for this reason because using eval is not safe.
Json's problem is that it can't save any type of data, it can save only standard objects, but if we're talking about not built-in types of data, you never know, what is at their .__repr__(), so there's no way to use repr-eval with this kind of data

So, there is no reverse function for all types of data, you can use repr-eval for built-in, but for built-in data the json library is better at least because it's safe

share|improve this answer

answered Mar 25 at 10:31

Kolay.NeKolay.Ne

7699 bronze badges

share|improve this answer

answered Mar 25 at 10:31

Kolay.NeKolay.Ne

7699 bronze badges

answered Mar 25 at 10:31

Kolay.NeKolay.Ne

7699 bronze badges

answered Mar 25 at 10:31

Kolay.NeKolay.Ne

7699 bronze badges