while-loop

问题 I would like to update a Label in my GUI to be a sort of progress bar, display how complete a data transfer is. Everywhere I look, people say to use the textvariable option of Label and then to set the string and the label updates. This does not work for me. The label updates at the end of the data collection loop. I don't know too much about programming in depth but I imagine that Python is not refreshing Tkinter until after it is finished with the data collection loop rather than mid loop.

问题 I am a beginner with Python and trying few programs. I have something like the following WHILE loop construct in Python (not exact). IDLE 2.6.4 >>> a=0 >>> b=0 >>> while a < 4: a=a+1 while b < 4: b=b+1 print a, b 1 1 1 2 1 3 1 4 I am expecting the outer loop to loop through 1,2,3 and 4. And I know I can do this with FOR loop like this >>> for a in range(1,5): for b in range(1,5): print a,b 1 1 1 2 .. .. .. .. // Other lines omitted for brevity 4 4 But, what is wrong with WHILE loop? I guess I

问题 While vs. do-while While and do-while are functionally equivalent when the blocks are empty , although while seems more natural: do {} while (keepLooping()); while (keepLooping()) {} One typical use case of a while/do-while with an empty block is to force an update of atomic objects with a compareAndSet (CAS). For example the code below will increment a in a thread-safe way: int i; AtomicInteger a = new AtomicInteger(); while (!a.compareAndSet(i = a.get(), i + 1)) {} Context Several parts of

问题 I have to write a function of the following method : Rejection method (uniform envelope) : Suppose that fx is non-zero only on [a, b], and fx ≤ k. Generate X ∼ U(a, b) and Y ∼ U(0, k) independent of X (so P = (X, Y ) is uniformly distributed over the rectangle [a, b] × [0, k]). If Y < fx(x) then return X, otherwise go back to step 1. rejectionK <- function(fx, a, b, K) { # simulates from the pdf fx using the rejection algorithm # assumes fx is 0 outside [a, b] and bounded by K # note that we

问题 I have a PHP script that seemed to stop running after about 20 minutes. To try to figure out why, I made a very simple script to see how long it would run without any complex code to confuse me. I found that the same thing was happening with this simple infinite loop. At some point between 15 and 25 minutes of running, it stops without any message or error. The browser says "Done". I've been over every single possible thing I could think of: set_time_limit ( session.gc_maxlifetime in the php

问题 I'm trying to use a while loop to add objects to a list. Here's basically what I want to do: class x: pass choice = raw_input(pick what you want to do) while(choice!=0): if(choice==1): Enter in info for the class: append object to list (A) if(choice==2): print out length of list(A) if(choice==0): break ((((other options)))) I can get the object added to the list, but I am stuck at how to add multiple objects to the list in the loop. Here is the code I have so far: print "Welcome to the

问题 I have my markup structure as below: <div> <div>value1</div> <div>value2</div> <div>value3</div> <div>value4</div> <div class="clear"></div> </div> <div> <div>value5</div> <div>value6</div> <div>value7</div> <div>value8</div> <div class="clear"></div> </div> I have my data in a PHP result set, let's say I have 9 records so the structure should be as below: <div> <div>value1</div> <div>value2</div> <div>value3</div> <div>value4</div> <div class="clear"></div> </div> <div> <div>value5</div>

问题 for() or while() - which is BEST? for (i=1; i<a; i++) /* do something */ OR i=1; while (i<a) { /* do something */ i++; } 回答1: The first is the idiomatic way; it is what most C coders will expect to see. However, I should note that most people will also expect to see for(i = 0; i < a; i++) Note that the loop starts at zero. This will do something a times. If you're going to write a while loop that is equivalent to a for loop as above I strongly encourage you to write it as a for loop. Again,

问题 I never thought this was possible, but read some conflicting comments and thought I would ask the experts. If I am progressing through a while loop that is reading a file line by line, is there a way to execute some code if the current iteration will be the final iteration in the loop? I understand that I could simply place this code immediately after the while loop, so that the code would execute after the last line, but I was just wondering if the iteration has any way of detecting it's

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 3 years ago . I'm making a digital clock in python for minecraft pi edition. I'm using a single while loop that contains a lot of code - it takes a short time to execute one run of it, but it's a few milliseconds more than I want, and this is wreaking havoc on my clock. Is there a way to make a while loop completely accurate?