constable 0.3.1

How does it work?

The constable.trace decorator uses Python’s Abstract Syntax Tree (AST) in much the same way we add print`(s) to debug states. During runtime, it prepares and inserts `print statements into the function’s AST after every assignment operation (ast.Assign, ast.AugAssign and ast.AnnAssign), and then executes the modified code in a separate namespace with exec.

$ pip install constable

Tested for python 3.8 and above.

Usage :

Tracking variables in a function

import constable

@constable.trace('a', 'b')
def example(a, b):
    a = a + b
    c = a
    a = "Experimenting with the AST"
    b = c + b
    a = c + b
    return a

example(5, 6)

Output :

constable: example: line 5
    a = a + b
    a = 11
    type(a) = <class 'int'>

constable: example: line 7
    a = "Experimenting with the AST"
    a = Experimenting with the AST
    type(a) = <class 'str'>

constable: example: line 8
    b = c + b
    b = 17
    type(b) = <class 'int'>

constable: example: line 9
    a = c + b
    a = 28
    type(a) = <class 'int'>

constable: example: line 3 to 10
    args: (5, 6)
    kwargs: {}
    returned: 28
    execution time: 0.00018480 seconds

Monitor functions

import constable

@constable.trace()
def add(a, b):
    return a + b

add(5, 6)

Output :

constable: add: line 3 to 5
    args: (5, 6)
    kwargs: {}
    returned: 11
    execution time: 0.00004312 seconds