How do I display all of one value from a nested list?

user_15686856 0
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If I have a nested list like this (the actual data will be a random length):

data = [['a', 'b', 'c', 'd'],['1', '2'],['3','4']]

How would I display only the first item in each list (a, 1, 3) using a loop.

for i in range(len(data)):
    print() #what goes here?
python
3 Answers
for i in range(len(data)):
    print(data[i][0])

or

for i in data:
    print(i[0])

This code will display the first value of nested list at index i. But I'm confused if those data will be stored in another list or tuple.

user_153596060

There are several ways.

To continue using an index like you currently are:

for i in range(len(data)):
    print(data[i][0])

In this method we get each nested array by accessing data[i] then access the first element of the nested array by accessing data[i][0].

However using an index to iterate through a list is not considered very pythonic; a more common way would be as follows:

for nestedArr in data:
    print(nestedArr[0])

By using in in this way each nested array is assigned to nestedArr, then we can access the first element of that nested array the same way as above.

Note:
Be careful to make sure that each element in data is actually a list and that each nested list has at least 1 element. You may wish to use an if statement and the len function to verify this before attempting to print the first element.

user_131623180

Shortest method is list comprehension:

print([e[0] for e in data])
user_95727800
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