在元组的单个元素上应用 function

Question

With a direct example it would be easier to understand

data = [(1995, 50.28), (1996, 28.52)]

result = [(1995, 50), (1996, 29)]

I would like to apply a transformation only on the second number of each tuple (50.28 and 28.52).

I saw the map() function that could help, but i think it works only on ALL elements, and having tuples inside list makes it a bit tricky

Answer 1

You can use lambda function inside map like this:

result = list(map(lambda x:(x[0], round(x[1])), data))

Output is:

[(1995, 50), (1996, 29)]

Answer 2

The more intuitive solution would be to iterate through the elements of the list, as many other answers noticed.

But if you want to use map , you can indeed but you need first to define a function that applies your desired transformation to the second element of each tuple:

data = [(1995, 50.28), (1996, 28.52)]

def round_second(tup):
    return tup[0], round(tup[1])

result = list(map(round_second, data))
result
>>> [(1995, 50), (1996, 29)]

Answer 3

You can use basic "for" loop. You can use like that;

data = [(1995, 50.28), (1996, 28.52)]

for i in range(0,len(data)):
    data[i] = list(data[i])
    data[i][1] = round(data[i][1])
    data[i]=tuple(data[i])

Answer 4

You can do this with a list comprehension and the built-in round() function as follows:

data = [(1995, 50.28), (1996, 28.52)]

result = [(x, round(y)) for x, y in data]

print(result)

Output:

[(1995, 50), (1996, 29)]

Answer 5

Map is what you need. Use it to apply a function on each tuple. That function would only interact with the second number of each tuple

def function(item):
    whatever(item[1])
    return item

data = [(1995, 50.28), (1996, 28.52)]
map(function, data)