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Is there a builtin way to reference a while loop condition without restating it?

Something like this: thing = None while not thing: thing = try_to_get_thing() if |reference loop condition|: #Same as if not thing time.sleep(TRYAGAIN_DELAY) I know I could just define the condition as a function, but this comes up often enough that I feel like there might be a builtin syntax for referencing the running loop's condition.

24th Apr 2024, 2:35 AM
Wilbur Jaywright
Wilbur Jaywright - avatar
10 Respuestas
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just for completeness: if we are using an assigment expression in a while loop header, we can also explicitely define the break condition like this : import random while (n := random.randint(0, 10)) != 7: print(n, end=", ") # all except 7 else: print(n) # 7 we have to enclose the first part of the expression in parenthesis, otherwise bolean values will be stored in variable `n`.
24th Apr 2024, 9:49 AM
Lothar
Lothar - avatar
+ 6
Wilbur Jaywright , An assignment expression using the "walrus" operator := might help. https://docs.python.org/3/reference/expressions.html#assignment-expressions This snippet prints random ints until it hits 0. Notice that the header of the while clause assigns a random int to n then uses the value of n as the condition, and you can reference n inside the suites of both the while clause and the else clause. import random while n := random.randint(-10, 10): print(n, end=" ") # non-0 else: print(n) # 0
24th Apr 2024, 4:18 AM
Rain
Rain - avatar
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In Python, there isn't a direct built-in way to reference the condition of a while loop without restating it. But, you can achieve similar functionality by using a flag variable within the loop. See this: https://stackoverflow.com/questions/68879241/stop-while-loop-w-variable-flag
24th Apr 2024, 4:19 AM
`–Ĺ—ā—āŠč®‚Āī‚Āį‚Ā∂
`–Ĺ—ā—āŠč®‚Āī‚Āį‚Ā∂ - avatar
24th Apr 2024, 4:41 AM
`–Ĺ—ā—āŠč®‚Āī‚Āį‚Ā∂
`–Ĺ—ā—āŠč®‚Āī‚Āį‚Ā∂ - avatar
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`–Ĺ—ā—āp‚Āī‚Āį‚Ā∂ , Glad you like it. I wasn't quite done. I have a bad habit of realizing I need to edit my comments immediately after I submit them. I edited the snippet to include equal likelihoods of negative and positive ints.
24th Apr 2024, 4:55 AM
Rain
Rain - avatar
+ 2
Wilbur Jaywright, OK: import random, time thing = None condition = not thing while condition: thing = random.randint(0,9) condition = 0<thing<5 print(thing) if condition: time.sleep(1) print("TRYAGAIN_DELAY") If it doesn't matter to you what happens after the last sleep command, then you don't need to write the "if condition" condition. And of course this code can be shortened using the operator ":=", as other participants in the discussion have already noted.
24th Apr 2024, 4:05 PM
Solo
Solo - avatar
+ 1
Solo in the given example, the delay before trying again to assign a non-nil value to ‚Äúthing‚ÄĚ is pointless if the first try was a success.
24th Apr 2024, 4:47 AM
Wilbur Jaywright
Wilbur Jaywright - avatar
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Lothar , Nice. That frees it up tremendously.
24th Apr 2024, 11:33 AM
Rain
Rain - avatar
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Lothar that looks like it will do what I wanted.
24th Apr 2024, 8:21 PM
Wilbur Jaywright
Wilbur Jaywright - avatar
0
What's the point of that? Why repeat the same condition twice? It's like writing: if true: if true: ...
24th Apr 2024, 3:21 AM
Solo
Solo - avatar