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POPython list([]) and []
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  1. POPython list([]) and []
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    copied!<pre><code>from cs1graphics import * from math import sqrt numLinks = 50 restingLength = 20.0 totalSeparation = 630.0 elasticityConstant = 0.005 gravityConstant = 0.110 epsilon = 0.001 def combine(A,B,C=(0,0)): return (A[0] + B[0] + C[0], A[1] + B[1] + C[1]) def calcForce(A,B): dX = (B[0] - A[0]) dY = (B[1] - A[1]) distance = sqrt(dX*dX+dY*dY) if distance &gt; restingLength: stretch = distance - restingLength forceFactor = stretch * elasticityConstant else: forceFactor = 0 return (forceFactor * dX, forceFactor * dY) #return a tuple def drawChain(chainData, chainPath, theCanvas): for k in range(len(chainData)): chainPath.setPoint(Point(chainData[k][0], chainData[k][1]),k) theCanvas.refresh() #refresh canvas chain = [] #chain here for k in range(numLinks + 1): X = totalSeparation * k / numLinks chain.append( (X,0.0) ) paper = Canvas(totalSeparation, totalSeparation) paper.setAutoRefresh(False) curve = Path() for p in chain: curve.addPoint(Point(p[0], p[1])) paper.add(curve) graphicsCounter = 100 somethingMoved = True while somethingMoved: somethingMoved = False oldChain = list(chain) #oldChain here for k in range(1, numLinks): gravForce = (0, gravityConstant) leftForce = calcForce(oldChain[k], oldChain[k-1]) rightForce = calcForce(oldChain[k], oldChain[k+1]) adjust = combine(gravForce, leftForce, rightForce) if abs(adjust[0]) &gt; epsilon or abs(adjust[1]) &gt; epsilon: somethingMoved = True chain[k] = combine(oldChain[k], adjust) graphicsCounter -= 1 if graphicsCounter == 0: drawChain(chain, curve, paper) graphicsCounter = 100 curve.setBorderWidth(2) drawChain(chain, curve, paper) </code></pre> <p>I was told that <code>list([]) == []</code>. So why is this code doing<br> <code>oldChain = list(chain)</code> instead of <code>oldChain = chain</code></p> <p>it's the same thing so it does not matter either way to do it?</p>
 

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