Index of item in a list of a list in python

Question

I got the following problem: I'm writing a script for Ensight (a program for visualizing CFD computations) in python. The program Ensight gives me a list for the time values like:

print ensight.query(ensight.TIMEVALS)['timevalues']
[[0, 0.0], [1, 9.99e-07], [2, 1.99e-06], [3, 0.0003],etc.]

Where the first value in every list is the timestep and the second value the actual time at this timestep. Now I want to ask somehow for timestep '2' and want to know the corresponding second value of the list. Therefore if I could just find the index of the timestep I could easily have the corresponding time value.

EDIT\\ It solved it now like this:

time_values = ensight.query(ensight.TIMEVALS)['timevalues']
for start,sublist in enumerate(time_values):
    if step_start in sublist:
        index_begin = start
for end,sublist in enumerate(time_values):
    if step_stop in sublist:
        index_end = end

MacDefender · Accepted Answer · 2013-10-31 07:12:04Z

1

Maybe this is what you want?

print ensight.query(ensight.TIMEVALS)['timevalues'][1][1]

That should print the 9.99e-07 as it is the second value in the second list included in your main list.

I'm just wondering why you have 3 opening and just 2 closing brackets. Is this a typo?

[[ [..].. ]

If you have a list like myList = [[0, 0.0], [1, 9.99e-07], [2, 1.99e-06], [3, 0.0003],etc.] you can access the first nested list with myList[0] resulting in [0, 0.0] To access the second value in that list you can use myList[0][1]

edited Oct 31, 2013 at 7:12

answered Oct 31, 2013 at 7:06

MacDefender

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1 Comment

Adrian Pfeifle Over a year ago

yes sorry, that was a typo! That is not what I want, because I'm generating a GUI where one can enter from which time step to which time step one wants to evaluate certain variables. And I want to prevent errors in case of the loaded CFD case file doesn't start with timestep = 0

funtime · Accepted Answer · 2013-10-31 07:13:22Z

1

Set n to the required timestep value

>>> n=2
>>> print [list[1] for list in ensight.query(ensight.TIMEVALS)['timevalues'] if list[0]=n ]

this can also be extended in your case

>>> from=2
>>> to=100
>>> print [list[1] for list in ensight.query(ensight.TIMEVALS)['timevalues'] if (list[0]>from && list[0]<to)  ]

answered Oct 31, 2013 at 7:13

funtime

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Siva Cn · Accepted Answer · 2013-10-31 07:13:39Z

1

>>> l = ensight.query(ensight.TIMEVALS)['timevalues']

>>> print l
[[0, 0.0], [1, 9.99e-07], [2, 1.99e-06], [3, 0.0003]]

>>> _d = {int(ele[0]): ele[1] for ele in l}

>>> print _d[2]
1.99e-o6

answered Oct 31, 2013 at 7:13

Siva Cn

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