pygritia package

Submodules

• pygritia.attr module
• pygritia.binary module
• pygritia.call module
• pygritia.cases module
• pygritia.cast module
• pygritia.core module
• pygritia.item module
• pygritia.lazy module
• pygritia.ops module
• pygritia.prop module
• pygritia.rbinary module
• pygritia.symbols module
• pygritia.unary module
• pygritia.util module

Module contents

Pygritia: Lazy Evaluation

• Build expressions naturally
• Evaluate expression with symbol substitution
• Create property by a expression with special symbol

>>> class Spam:
...     egg = [42]
...     foo = this.egg[0]
>>> spam = Spam()
>>> print(this.egg * 2)
this.egg * 2
>>> evaluate(this.egg * 2, {this: spam})
[42, 42]
>>> spam.foo
42
>>> spam.foo = 9
>>> spam.egg
[9]

pygritia.evaluate(expr: _T, namespace: Mapping[Union[str, LazyMixin], Any]) → _T

Evaluate lazy expression

Evaluate expression with symbol substitution according to given namespace

Parameters:

• expr –

  Lazy expression or evaluated value

  If given value is not a lazy expression, this function returns it immediately

• namespace –

  Symbol table which will be used in substitution

  The key of table can be both of string and symbol expression

Returns:

Evaluated value

pygritia.lazy_call(func: _T) → _T

Make a function to support lazy expression

>>> from pygritia import this, lazy_call, evaluate
>>> @lazy_call
... def hello(obj):
...     print(obj)
>>> print(hello(this))
hello(this)
>>> hello("123")
123
>>> evaluate(hello(this), {this: "123"})
123

pygritia.lazy_delattr(obj, name)

Deletes the named attribute from the given object.

delattr(x, ‘y’) is equivalent to ``del x.y’‘

pygritia.lazy_delitem(a, b)

Same as del a[b].

pygritia.lazy_getattr()

getattr(object, name[, default]) -> value

Get a named attribute from an object; getattr(x, ‘y’) is equivalent to x.y. When a default argument is given, it is returned when the attribute doesn’t exist; without it, an exception is raised in that case.

pygritia.lazy_getitem(a, b)

Same as a[b].

pygritia.lazy_setattr(obj, name, value)

Sets the named attribute on the given object to the specified value.

setattr(x, ‘y’, v) is equivalent to ``x.y = v’‘

pygritia.lazy_setitem(a, b, c)

Same as a[b] = c.

pygritia.symbol(name: str) → Any

Create symbol for lazy expression

Returns:Newly created symbol expression Return type:Any

pygritia.update(expr: _T, val: _T, namespace: Mapping[Union[str, LazyMixin], Any]) → None

Update the value of lazy expression

Set the value of lazy expression to the given val Only assignable expression can be updated. ex) this[3], this.spam

Parameters:

• expr – Assignable lazy expression
• val – New value
• namespace –

  Symbol table which will be used in substitution

  The key of table can be both of string and symbol expression

pygritia.this

pygritia.If(cond: bool, value: _T) → Optional[_T]

value if cond else None

pygritia.IfThenElse(cond: bool, true: _T, false: _U) → Union[_T, _U]

true if cond else false

pygritia.Case(cond: _T, cases: Mapping[_T, _U], default: _U) → _U

cases.get(cond, default)

pygritia.Ensure(obj: Optional[_T], default: _T) → _T

obj if obj is not None else default

pygritia.is_none(obj: Any) → bool

obj is None

pygritia.lazy_cast(target_type: Callable[[_T], _U], expr: _T, expr_type: Optional[Callable[[_U], _T]] = None) → _U

Create automatic casting lazy expression

Parameters:

• target_type – Converter from expression type to result type
• expr – Target expression
• expr_type –

  Converter from result type to expression type

  If it is omitted, the constructor of evaluated expr will be used.

Returns:

Casting expression