kevin parks wrote:
<div class="moz-text-flowed" style="font-family: -moz-fixed">Back to
python after a long long layoff. So i am running into some beginner's
confusion...
I am trying to plot a list of numbers in gnuplot.py. To do that I am
trying to pack the list with an index by iterating over the list so i
can get something like:
foo = [12, 11, 9, 6, 2, 9, 3, 8, 12, 3, 5, 6]
[ [1, 12], [2, 11], [3, 9], [4, 6], [5, 2], [6, 9], [7, 3], [8, 8] ... ]
So that i have x, y pairs to plot. When i print in my func i get the
right thing, for each item (note scaffolding) yet when i reurn the
whole list i just get the last pair repeated over and over.
I am not sure why this is.
def pack(in_seq):
out_list=[]
x = 1
ll=[1, 1]
for each in in_seq:
ll[0] = x
ll[1] = each
out_list.append(ll)
#print ll
x = x + 1
print out_list
# function declarations would go here
def test():
"""test function - say what this does here and skip a line
Keyword arguments:
none
"""
print
foo = minus(200)
plot_me = pack(foo)
#print foo
print
print plot_me
if __name__ == "__main__":
test()
</div>
Your specific problem is that you're not building new lists, you're just
reusing the same one each time through the loop. The most brute-force
fix for the problem is to use the slice operator to make a copy of the
list before appending it to the outer list.
def pack(in_seq):
out_list=[]
x = 1
ll=[1, 1]
for each in in_seq:
ll[0] = x
ll[1] = each
out_list.append(ll[:]) #make a copy of ll, and append
that copy
#print ll
x = x + 1
print out_list
pack(in_seq)
#But that's not efficient. Better would be to construct a new list each
time (and I'm going to avoid using variables that look like numbers):
def pack(in_seq):
out_list=[]
x = 1
for each in in_seq:
item = [x, each]
out_list.append(item)
#print ll
x = x + 1
print out_list
pack(in_seq)
#or even:
def pack(in_seq):
out_list=[]
x = 1
for each in in_seq:
out_list.append( [x, each] )
#print ll
x = x + 1
print out_list
pack(in_seq)
#Note that there's a useful function enumerate which could help here:
def pack(in_seq):
out_list=[]
for x, each in enumerate(in_seq):
item = [x+1, each] #(too bad you want your integers to
start at 1; Python likes zero-based
out_list.append(item)
#print ll
print out_list
pack(in_seq)
#and that could be simplified further
def pack(in_seq):
out_list=[]
for item in enumerate(in_seq):
item = list(item) #turn the tuple into a list
item[0] += 1 #because you're 1-based instead of zero-based
out_list.append(item)
#print ll
print out_list
pack(in_seq)
#and one more step, using zip() to combine two lists
def pack(in_seq):
out_list = zip(xrange(1, 1+len(in_seq)), in_seq)
print out_list
pack(in_seq)
HTH
DaveA
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