On 2012-08-14 17:38, light1qu...@gmail.com wrote:
Hi, I am migrating from PHP to Python and I am slightly confused.
I am making a function that takes a startingList, finds all the strings in the
list that begin with 'x', removes those strings and puts them into a xOnlyList.
However if you run the code you will notice only one of the strings beginning
with 'x' is removed from the startingList.
If I comment out 'startingList.remove(str);' the code runs with both strings
beginning with 'x' being put in the xOnlyList.
Using the print statement I noticed that the second string that begins with 'x'
isn't even identified by the function. Why does this happen?
def testFunc(startingList):
xOnlyList = [];
for str in startingList:
if (str[0] == 'x'):
print str;
xOnlyList.append(str)
startingList.remove(str) #this seems to be the problem
print xOnlyList;
print startingList
testFunc(['xasd', 'xjkl', 'sefwr', 'dfsews'])
#Thanks for your help!
You might find the following useful:
def testFunc(startingList):
xOnlyList = []; j = -1
for xl in startingList:
if (xl[0] == 'x'):
xOnlyList.append(xl)
else:
j += 1
startingList[j] = xl
if j == -1:
startingList = []
else:
del startingList[j:-1]
return(xOnlyList)
testList1 = ['xasd', 'xjkl', 'sefwr', 'dfsews']
testList2 = ['xasd', 'xjkl', 'xsefwr', 'xdfsews']
testList3 = ['xasd', 'jkl', 'sefwr', 'dfsews']
testList4 = ['asd', 'jkl', 'sefwr', 'dfsews']
xOnlyList = testFunc(testList1)
print 'xOnlyList = ',xOnlyList
print 'testList = ',testList1
xOnlyList = testFunc(testList2)
print 'xOnlyList = ',xOnlyList
print 'testList = ',testList2
xOnlyList = testFunc(testList3)
print 'xOnlyList = ',xOnlyList
print 'testList = ',testList3
xOnlyList = testFunc(testList4)
print 'xOnlyList = ',xOnlyList
print 'testList = ',testList4
And here is another version using list comprehension that I prefer
testList1 = ['xasd', 'xjkl', 'sefwr', 'dfsews']
testList2 = ['xasd', 'xjkl', 'xsefwr', 'xdfsews']
testList3 = ['xasd', 'jkl', 'sefwr', 'dfsews']
testList4 = ['asd', 'jkl', 'sefwr', 'dfsews']
def testFunc2(startingList):
return([x for x in startingList if x[0] == 'x'], [x for x in
startingList if x[0] != 'x'])
xOnlyList,testList = testFunc2(testList1)
print xOnlyList
print testList
xOnlyList,testList = testFunc2(testList2)
print xOnlyList
print testList
xOnlyList,testList = testFunc2(testList3)
print xOnlyList
print testList
xOnlyList,testList = testFunc2(testList4)
print xOnlyList
print testList
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