CODEWITHSUNDEEP
pythonlistmatplotlib
Gabriel
Gabriel

Reputation: 42459

Cycle through elements in list to assign different colors to plot

I have a main list made of N sub-lists (where this number will change for different runs), each one containing pairs of x,y points. I need a way to plot the points in these sub-lists with different colors, taken from a list with (usually) fewer elements than sub-lists. To do this I need a way to cycle through this list of colors. This is an excerpt of what I'm after:

# Main list which holds all my N sub-lists.
list_a = [[x,y pairs], [..], [..], [..], ..., [..]]

# Plot sub-lists with colors taken from this list. I need the for block below
# to cycle through this list.
col = ['red', 'darkgreen', 'blue', 'maroon','red']

for i, sub_list in enumerate(list_a):
    plt.scatter(sub_list[0], sub_list[1], marker='o', c=col[i])

If len(col) < len(list_a) (which will happen most of the time) this will return an error. Since for a given run of my code the number of sub-lists will vary, I can't hard code a number of colors into the col list, so I need a way to cycle through that list of colors. How could I do that?

Upvotes: 0

Views: 1931

Answers (2)

thefourtheye
thefourtheye

Reputation: 239683

You can use modulo operator 

numberOfColors = len(col)
for i, sub_list in enumerate(list_a):
    plt.scatter(sub_list[0], sub_list[1], marker='o', c=col[i % numberOfColors])

Upvotes: 4

DSM
DSM

Reputation: 353569

IIUC, you can use itertools.cycle, and then instead of c=col[i], use next. For example:

>>> from itertools import cycle
>>> cols = cycle(["red", "green", "blue"])
>>> next(cols)
'red'
>>> next(cols)
'green'
>>> next(cols)
'blue'
>>> next(cols)
'red'

Upvotes: 7

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