sconst

Immutable constant types for Python.

Installation

pip install sconst

Usage

Constant types

from sconst import IntConstant, StrConstant, ListConstant, TupleConstant

x = IntConstant(42)
print(x.value)   # 42
x.value = 10     # raises ChangeConstError

s = StrConstant("hello")
print("ell" in s)  # True
s + " world"       # raises ChangeConstError

items = ListConstant([1, 2, 3])
print(items[0])    # 1
for item in items: # iteration works
    print(item)

coords = TupleConstant((10, 20))
print(len(coords)) # 2

const_property descriptor

A read-only property whose value is computed once and then frozen:

from sconst import const_property

class Config:
    @const_property
    def max_retries(self):
        return 5

cfg = Config()
cfg.max_retries        # 5
cfg.max_retries = 10   # raises ChangeConstError
del cfg.max_retries    # raises DeleteConstError

Classes

Class	Description
BaseConstant	Base class for all constant wrappers
IntConstant	Constant integer — blocks arithmetic and mutation
StrConstant	Constant string — blocks +, *, and item assignment
IterableConstant	Base for iterable constants — supports iteration, indexing, len(), and in
ListConstant	Constant list
TupleConstant	Constant tuple

Exceptions

Exception	Raised when
SconstException	Base exception for all sconst errors
ChangeConstError	An attempt is made to modify a constant
DeleteConstError	An attempt is made to delete a constant attribute

License

MIT