Filter list of lists in Python by element value

Question

Suppose I have a list lines where every element is a list

['2015', 'Friday', 9.94, 0.0]
['2015', 'Tuesday', 10.54, 0.002615]
['2015', 'Wednesday', 9.86, -0.001531]
['2016', 'Monday', 10.41, 0.007841]
['2016', 'Thursday', 11.51, 0.006415]
['2017', 'Tuesday', 8.74, -0.003711]
['2017', 'Friday', 12.62, 0.008516]

How would I filter out the list if, for example, I wanted to get all the elements where the first element of a list is 2016 and the second element is Monday? Think of this as filtering out a pandas dataframe by column values, but using a list of lists.

Asked By: Vadim Katsemba

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Source

Answer 1

Just use a list comprehension with condition:

>>> [x for x in lst if x[0] == '2016' and x[1] == "Monday"]
[['2016', 'Monday', 10.41, 0.007841]]

Answered By: tobias_k

Answer 2

Using list comprehension which contains conditional statements.

lines = [
    [2015, "Friday", 9.94, 0.0],
    [2015, "Tuesday", 10.54, 0.002615],
    [2015, "Wednesday", 9.86, -0.001531],
    [2016, "Monday", 10.41, 0.007841],
    [2016, "Thursday", 11.51, 0.006415],
    [2017, "Tuesday", 8.74, -0.003711],
    [2017, "Friday", 12.62, 0.008516]
]
requiredLine = [line for line in lines if line[0] == 2016 and line[1] == "Monday"]
print(requiredLine)

Answered By: Vyshak Puthusseri

Answer 3

I would separate the selection logic from the following filtering:

def func(x):
    return x[0] == '2016' and x[1] == "Monday"

list(filter(func, your_data))

Answered By: nikeros

Filter list of lists in Python by element value

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