Does Python have lazy evaluation?
Yes, Python evaluates boolean conditions lazily. The docs say, The expression x and y first evaluates x; if x is false, its value is returned; otherwise, y is evaluated and the resulting value is returned.
What is lazy evaluation?
In programming language theory, lazy evaluation, or call-by-need, is an evaluation strategy which delays the evaluation of an expression until its value is needed (non-strict evaluation) and which also avoids repeated evaluations (sharing).
What is a lazy function Python?
In a nutshell, lazy evaluation means that the object is evaluated when it is needed, not when it is created. In Python 2, range will return a list – this means that if you give it a large number, it will calculate the range and return at the time of creation: >>> i = range(100) >>> type(i)
Does NumPy do lazy evaluation?
lazyarray is a Python package that provides a lazily-evaluated numerical array class, larray , based on and compatible with NumPy arrays.
Are Python generators lazy?
Generators are memory efficient since they only require memory for the one value they yield. Generators are lazy: they only yield values when explicitly asked.
What is lazy variable in Python?
Lazy initialization of a Python object means that it is initialized when it is created for the first time, or the result of the first creation is saved, and then the result is returned directly every time it is called.
What is lazy evaluation example?
Lazy evaluation is an evaluation strategy which holds the evaluation of an expression until its value is needed. It avoids repeated evaluation. Haskell is a good example of such a functional programming language whose fundamentals are based on Lazy Evaluation.
How does Haskell lazy evaluation work?
Lazy evaluation is a method to evaluate a Haskell program. It means that expressions are not evaluated when they are bound to variables, but their evaluation is deferred until their results are needed by other computations.
How is lazy evaluation implemented?
To implement lazy evaluation in our interpreter we need to modify the applica- tion expression evaluation rule to delay evaluating the operand expressions until they are needed. To do this, we introduce a new datatype known as a thunk. We define a Python class, Thunk for representing thunks.
What is lazy list Python?
A lazy list is an iterator that behaves like a list and possesses a cache mechanism. A lazy list is potentially infinite and speed performances of the cache is comparable with Python lists. One major difference with original Python list is that lazy list are immutable.
How are Haskell expressions evaluated?
An expression is evaluated by normal order (leftmost outermost redex first). To avoid unnecessary computation, normal order reduction chooses to apply the function rather than first evaluating the argument.
What is lazy evaluation Haskell?
From HaskellWiki. Lazy evaluation is a method to evaluate a Haskell program. It means that expressions are not evaluated when they are bound to variables, but their evaluation is deferred until their results are needed by other computations.
Is there a way to prove Python is lazy?
Python’s laziness can be proved by the following code: would cause both ‘foo’ and ‘bar’ to be printed. Show activity on this post. This isn’t technically lazy evaluation, it’s short-circuit boolean expressions. Lazy evaluation has a somewhat different connotation. For example, true lazy evaluation would likely allow this But Python doesn’t.
Why doesn’t Python have lazy evaluation for boolean arguments?
This isn’t technically lazy evaluation, it’s short-circuit boolean expressions. Lazy evaluation has a somewhat different connotation. For example, true lazy evaluation would likely allow this But Python doesn’t. Python is also nice in that it “echos” it’s boolean arguments.
What is the difference between strict and lazy evaluation?
This process is called Evaluation and it needs some sort of computation power. In this case, the evaluation is done immediately, therefore it has another name: Strict Evaluation. On the other hand, we have a non-strict evaluation which is called Lazy Evaluation.