列表中的嵌套元组

Question

I have a list of lists of tuples and am having trouble accessing the values within the tuples.

Note: apologies for the basic nature of this query, but I'm a beginner and it takes me a long time to access simple variables.

E.g: 

[[('foo', '-1')],[('bar', '-5'),('baz', '+7')], [('qux', '+9')]]

I want to 1) remove the second value of each tuple ie the numbers and 2) remove the tuple type and just convert it a list of strings.

As you can see, it is a list of tuples so it can be one tuple or a number of tuples based on the content of extraction - but it is always 2 values within each tuple and I want to remove the second value.

I am having trouble 1) converting each tuple to a string, to be able to 2) remove the second value (preferably I want to remove that before making it into a string) - any ideas?

Answer 1

I don't understand very well the question but two points:

1. Your values in tuple are already string.

2. To access tuple, you can iterate over your list and access first value of tuple by doing this:

tuple[0]

I don't understand if you have a list of list of tuple, or a list of tuple

Answer 2

Just get 0 index of each tuple by iterating in list

ll_tuple = [[('foo', '-1')],[('bar', '-5'),('baz', '+7')], [('qux', '+9')]]
print(
    [
        [tuple_[0] for tuple_ in l_tuple]
        for l_tuple in ll_tuple
    ]
)

Answer 3

First of all your list of lists of tubles is incorrectly formatted I assume what you mean:

data = [
    [('foo', '-1')],
    [('bar', '-5')],
    [('baz', '+7'), ('qux', '+9')]
]

When create a nested for loop and append the first element in each tuble to new list output.

output = []
for lst in data:
   for tub in lst:
      output.append(tub[0])
print(output)

Prints:

['foo', 'bar', 'baz', 'qux']