Python「如果超過最大步數，打破循環」

我正在研究一個（非常複雜和不雅）Python代碼，通過蠻力3色圖形，並且在我的主代碼塊I' m試圖包含一個聲明，說「如果通過循環的最大運行次數超過（某些任意數量），跳出第一個（while a in range(0,len(vertices))）循環」。Python「如果超過最大步數，打破循環」

a = 0 
steps = 0 
while a in range(0,len(vertices)): 
    for j in newdict: 
     steps+=1  #count number of times it goes through the loop 
     print(steps) 
     if a>=len(vertices) or steps>=100000: 
      break  #this is where my error is occurring 

     i = vertices[a] 
     if dict1[i[0]]==dict1[i[1]] and (list(dict1.values()))!=j: #if the adjacent vertices are the same color and we have not cycled back to our original dict1, 
      dict1[i[1]]=colors[dict1[i[1]]+1] #change color of the second vertex 
      a = 0 #after a vertex is changed colors, I don't want it to keep going: I want the code to stop and reexamine from the top with this new value 
      newdict.append(list(dict1.values())) #running list of all previous dictionaries (attempted colorings): if our dictionary ever cycles through to something it already was, try again 
      check = all(dict1[i[0]] != dict1[i[1]] for i in vertices) # check all adjacent vertices are different colors 
      if not check: 
       continue 
      elif check: 
       break #at any point throughout the code, if the graph is colorable, break the loop and jump to end instead of continuing to color 
     elif dict1[i[0]]==dict1[i[1]]: #if we do eventally cycle back to our original dict1, now we'll try changing the first vertex color 
      dict1[i[0]] = colors[dict1[i[0]] + 1] 
      a = 0 
      newdict.append(list(dict1.values())) 
      check = all(dict1[i[0]] != dict1[i[1]] for i in vertices) # check all adjacent vertices are different colors 
      if not check: 
       continue 
      elif check: 
       break #at any point throughout the code, if the graph is colorable, break the loop and jump to end instead of continuing to color 
     else: 
      a+=1

然而，我發現，即使超過10步經過（這是我所看到的，我打印的步數），循環不打破，成爲一個無限循環，而且數量步驟繼續超過100000.我應該包括另一個循環，

while steps < 100000:

而不是隻是添加另一個條件，我的第一個循環？我是在犯一個語法錯誤還是對我的代碼更深入的問題？

（完整的代碼可以here。）

來源

2017-03-03 Emma Krentz

您還沒有描述錯誤。你期望打破哪一個循環？你怎麼知道它確實或不休息？等等 – pvg

謝謝！我做了一些編輯。希望這更清楚。 –

您可以將'steps'條件添加到while條件中，這樣在你離開內部循環後，while將不會繼續。 break只會讓你離開內部循環。 – pvg

你有兩個循環

while a in range(0,len(vertices)): # Loop 1 
    for j in newdict: # Loop 2 
     steps+=1  #count number of times it goes through the loop 
     print(steps) 
     if a>=len(vertices) or steps>=100000: 
      break  #this is where my error is occurring

所以當你break，它打破內部循環，這是for j in newdict:你有另一個條件添加到break循環while

來源

2017-03-03 19:14:08 Nilesh

謝謝，我完全錯過了！我在我的第一個'while'循環中包含'steps'條件，並且它工作正常。 –

在while語句中添加另一個條件，然後在中斷之前設置此條件。

max = False 
while a in range(0,len(vertices)) and not max: 
... 
    for j in newdict: 
     ... 
     if a>=len(vertices) or steps>=100000: 
      max = True 
      break  #this is where my error is occurring

來源

2017-03-03 19:30:51 wwii

Python「如果超過最大步數，打破循環」

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