Convert any Python expression to a string

[voidtrance]

I'd like to be able to convert any Python expressions to a string. Something like this:

def show(a):
    print(stringify(a))

>>> show(5 + 4)
"5 + 4"

In C, the above is pretty easy but it uses pre-processor macros. But to my knowledge, in Python the expressions 5 + 4 is evaluated before the show() function is even called.

However, before giving up, I wanted to ask if there might be some trick with inspect or ast that might work.

[Pedroski55]

Why on earth would you want to do this? The method depends on where you are getting the expressions and the values you want as a string.

A Python script is a just a text file, just a string, so if you want to find arithmetical expressions in a text file, do this:

import re

# a Python script is just a text file
# if the expressions are statically assigned in a Python script
# use a regex to find arithmetical expressions or anything else

# look for 1 or more numbers, followed by space and or an operator followed by at least 1 number
maths = re.compile(r'([0-9]+)([\s+/*-]+)([0-9]+)')
# how this works example
line = 'e = 5 + 4'
res = maths.search(line)
res.groups() # returns ('5', ' + ', '4')

path2text = '/home/peterr/PVE/quatsch.py'

with open(path2text) as infile:
    text_list = infile.readlines()

for line in text_list:
    res = maths.search(line)
    if res:
        print(line, res.groups())

Gives:

Output:
e = 5 + 4
 ('5', ' + ', '4')
print(5 + 4)
 ('5', ' + ', '4')
d = '5 + 4'
 ('5', ' + ', '4')

If you are assigning the variables dynamically:

# print(5 + 4) will print 9
# if you are dynamically assigning the variables, the result of input() is already a string:
arithmetic = input('Enter a number, an operator and another number, separated by a space ... ').split()
print(' '.join(arithmetic))

Output:
5 + 4

If you statically assign individual values:

# if you assign individual values as integers
a = 5
b = 4
# you can't str(+) you will get an error
operator = input('Enter the operator you want to use ... ')
c = str(a) + operator + str(b)
print(c)

[DeaD_EyE]

I'd like to be able to convert any Python expressions to a string. Something like this:

def show(a):
    print(stringify(a))

>>> show(5 + 4)
"5 + 4"

The object a is evaluated, before it's called with the function. There are ways to get the last stackframe, but you won't get the source code of it, if it's not a function.

What you could do is disassemble the source code:

PS C:\Users\xxxx> py -3.13 -m dis .\s.py
  0           RESUME                   0

  1           LOAD_CONST               0 (<code object show at 0x000002943B5CD230, file ".\s.py", line 1>)
              MAKE_FUNCTION
              STORE_NAME               0 (show)

  4           LOAD_NAME                0 (show)
              PUSH_NULL
              LOAD_CONST               1 (9)
              CALL                     1
              POP_TOP
              RETURN_CONST             2 (None)

Disassembly of <code object show at 0x000002943B5CD230, file ".\s.py", line 1>:
  1           RESUME                   0

  2           LOAD_GLOBAL              1 (print + NULL)
              LOAD_GLOBAL              3 (stringify + NULL)
              LOAD_FAST                0 (a)
              CALL                     1
              CALL                     1
              POP_TOP
              RETURN_CONST             0 (None)

ATM, I'm at work and have to use Windows....

On Linux, you just call: python3 -m dis ./s.py