select sub item in a tuple list in python

Question

Here I have one list like this:

a = [[13245,0.123],[12435,0.435],[12345,0.799],[98775,0.573]...]

I want to use the first item in every tuple as x axis, and the second item in every tuple as y axis to plot a figure.

like x = [13245,12435,12345,68775] y = [0.123,0.435,0.799,0.573]

How can I select them out?

Answer 1

最简单的方法可能是使用zip ：

x, y = zip(*a)

Answer 2

Try this:

x = [tmplist[0] for tmplist in a]
y = [tmplist[1] for tmplist in a]

Also, [] doesn't define tuples, but lists. But in your case the handling is equal.

Answer 3

use:

x = []
y = []
for e in a:
    x.append(e[0])
    y.append(e[1])

edit: I didn't even remeber zip(), but it is certainly the best way of doing it:

x, y = zip(*a)

Answer 4

python have a realy powerfull function for this :)

zip

try it

x,y = zip(*a)

the * is the key. see the doc for more details

Answer 5

I'm not sure why your converting to ax list and ay list to plot coordinates. Would something as simple as this work?

for x,y in a:
  plot(x,y)