iterate over a list of list in python

Question

I have a list of the following type. I want to normalize this list using the function I have written. for example- normalize (). I want to pass the second innermost list to the normalize(). I want to do it one list at a time.

 [[['179.0', '77.0'],
  ['186.0', '93.0'],
  ['175.0', '72.0'],
  ['195.0', '68.0']],
 [['178.0', '76.0'],
  ['185.0', '93.0'],
  ['164.0', '91.0'],
  ['155.0', '117.0']],
  ['161.0', '127.0'],
  ['191.0', '200.0'],
  ['190.0', '241.0'],
  ['194.0', '68.0']],
 [['176.0', '77.0'],
  ['183.0', '93.0'],
  ['163.0', '91.0'],
  ['155.0', '117.0']]......]

The code I tried normalizes the whole list. I want to do it row-wise. I have tried following

normalized_data = [normalize3(data) for data in load_pose_data()]

I would appreciate any help. Thank you

Next is second innermost? [['179.0', '77.0'], ['186.0', '93.0'], ['175.0', '72.0'], ['195.0', '68.0']]? — atline
– atline, Commented Oct 29, 2018 at 5:27

chenchuk · Accepted Answer · 2018-10-29 05:25:44Z

1

You can use list comprehension to achive that.

example:

# example function that add element to a list
def f(x):
    return x+[10]

outer_list = [[1,2],[3,4],[5,6]]

# this calls the function on each element
after = [ f(n) for n in outer_list ]

after
[[1, 2, 10], [3, 4, 10], [5, 6, 10]]

answered Oct 29, 2018 at 5:25

chenchuk

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1 Comment

sam Over a year ago

if I need one list at a time and keep using f(n) on the subsequent list one by one as mentioned in my post. Do I need to use a loop?

U13-Forward · Accepted Answer · 2018-10-29 05:28:08Z

1

In Addition to @chenshuk's answer, use lambda:

# example function that add element to a list
f=lambda x: x+[10]
outer_list = [[1,2],[3,4],[5,6]]
# this calls the function on each element
after = [ f(n) for n in outer_list ]

Use list comprehension.

Or do map:

So instead of (list comprehension):

after = [ f(n) for n in outer_list ]

Do:

after = list(map(f,outer_list))

Both cases:

print(after)

Is:

[[1, 2, 10], [3, 4, 10], [5, 6, 10]]

answered Oct 29, 2018 at 5:28

U13-Forward

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1 Comment

sam Over a year ago

I want to give this list by index so that the function will normalize(already written) the data for each index and predict(already written the function logic) for each index.

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