How can I access each element of a pair in a pair list?

Question

I have a list called pairs.

pairs = [("a", 1), ("b", 2), ("c", 3)]

And I can access elements as:

for x in pairs:
    print x

which gives output like:

('a', 1) ('b', 2) ('c', 3)

But I want to access each element in each pair, like in c++, if we use pair<string, int>
we are able to access, first element and second element by x.first, and x.second.eg.

x = make_pair("a",1)
x.first= 'a'
x.second= 1

How can I do the same in python?

Asked By: impossible

||

Source

Answer 1

Use tuple unpacking:

>>> pairs = [("a", 1), ("b", 2), ("c", 3)]
>>> for a, b in pairs:
...    print a, b
... 
a 1
b 2
c 3

See also: Tuple unpacking in for loops.

Answered By: alecxe

Answer 2

A 2-tuple is a pair. You can access the first and second elements like this:

x = ('a', 1) # make a pair
x[0] # access 'a'
x[1] # access 1

Answered By: Jayanth Koushik

Answer 3

If you want to use names, try a namedtuple:

from collections import namedtuple

Pair = namedtuple("Pair", ["first", "second"])

pairs = [Pair("a", 1), Pair("b", 2), Pair("c", 3)]

for pair in pairs:
    print("First = {}, second = {}".format(pair.first, pair.second))

Answered By: Hugh Bothwell

Answer 4

When you say pair[0], that gives you ("a", 1). The thing in parentheses is a tuple, which, like a list, is a type of collection. So you can access the first element of that thing by specifying [0] or [1] after its name. So all you have to do to get the first element of the first element of pair is say pair[0][0]. Or if you want the second element of the third element, it’s pair[2][1].

Answered By: henrebotha

Answer 5

You can access the members by their index in the tuple.

lst = [(1,'on'),(2,'onn'),(3,'onnn'),(4,'onnnn'),(5,'onnnnn')]

def unFld(x):

    for i in x:
        print(i[0],' ',i[1])

print(unFld(lst))

Output :

1    on

2    onn

3    onnn

4    onnnn

5    onnnnn

Answered By: Nikunj Parmar

Answer 6

I don’t think that you’ll like it but I made a pair port for python 🙂
using it is some how similar to c++

pair = Pair
pair.make_pair(value1, value2)

or

pair = Pair(value1, value2)

here’s the source code
pair_stl_for_python

Answered By: Baraa Al-Masri

How can I access each element of a pair in a pair list?

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