decorators.require

Summery

• decorator require_condition

For usage in a class, let's you set a condition in which a method is allowed to be called

• decorator once

Functions decorated with once either always return the result of the 1st call or raise an error if called a 2nd time

• decorator limit

Functions decorated with limit are allowed to be called on set amount of times

• decorator try_times

Functions decorated with try_times will be called several times if they raise an error

Contains

require_condition

from pyuseful.decorators.require import require_condition

class Test:
    # this style definition checks if the bool() of var is True
    require_ready = require_condition("ready")

    #  this style uses eval() to check condition ('self.a>=self.b' in this example)
    require_big_a = require_condition("a", ">=self.b")

    # you can ommit the first arg and just use `cond`, 'msg' let's you specify error message 
    require_big_b = require_condition(cond="self.b>=self.a", msg="'b' must be equal or bigger than 'a'")


    def __init__(self):
        self.ready = False
        self.a = 0
        self.b = 2
    

    def set_ready(self):
        self.ready = True

    @require_ready
    @require_big_b
    def inc_a(self):
        self.a += 1
    
    @require_ready
    @require_big_a
    def inc_b(self):
        self.b += 1

t = Test()
# t.inc_a()   # bool(ready) == False -> will raise an error 
t.set_ready()    
t.inc_a()     # b>=a == True -> a=1, b=2
# t.inc_b()   # a>=b == False -> will raise an error
t.inc_a()     # b>=a == True -> a=2, b=2
t.inc_b()     # a>=b == True -> a=2, b=3

---

once

from pyuseful.decorators.require import once

# will always return the 1st called value
@once
def fun1(a):
    return a

# will raise an error on the 2nd call
@once(mode="error")
def fun2(a):
    return a

print(fun1(1))  # will print '1'
print(fun1(2))  # will still print '1'

print(fun2(1)) # will print '1'
# print(fun2(2)) # this will raise an error

---

limit

from pyuseful.decorators.require import limit

@limit(2)
def fun():
    print("hi")

fun()  # 1st call is allowed
fun()  # 2nd call is allowed
# fun()  # 3rd call, this will raise an error

try_times

from pyuseful.decorators.require import try_times

# will try calling fun1 2 times, 1st call raises an error
x = -1
@try_times(2)
def fun1(a):
    global x
    x += 1
    b = 1/x
    return b

a = fun1(10)
print(a) # will print '1.0'