Checking an element in a list of tuples using the in command, only one parameter observed in python

Question

How to check if a tuple is contained in a list using the property in. Example:

lista = [('joao', 13), ('maria', 20), ('carlos', 30)]

I want to know if carlos is on the list

Answer 1

A simple way with in would be:

lista = [('joao', 13), ('maria', 20), ('carlos', 30)]

"carlos" in [x[0] for x in lista]
True

UPDATING:

According to Anderson’s comment, it would look better as follows:

lista = [('joao', 13), ('maria', 20), ('carlos', 30)]

"carlos" in (x[0] for x in lista)
True

You can see the difference like this:

(x[0] for x in lista)
<generator object <genexpr> at 0x7ff4fc1af840>

[x[0] for x in lista]
['joao', 'maria', 'carlos']

Answer 2

To use the operator in in this search, you can use a list comprehension to turn your list with names and initial integers into a list with only names, as Ricardo mentioned, which can be considered the most idiomatic of the Python language:

names_and_ints = [('joao', 13), ('maria', 20), ('carlos', 30)]
only_names = [tpl[0] for tpl in names_and_ints]

"carlos" in only_names
>>> True

Or you can use a for traditional, which is also easy to understand:

names_and_ints = [('joao', 13), ('maria', 20), ('carlos', 30)]
only_names = []
for name, _ in names_and_ints:
   only_names.append(name)

"carlos" in only_names
>>> True

Remembering that both methods save the list in memory, a fact that can be problematic if such a list is too large.