Filter a list of tuples based on condition

Question

I have a list like this:

A=[(1,\'A\'),(2,\'H\'),(3,\'K\'),(4,\'J\')]

Each member of this list is like this: (number, string)

Now i

Answer 1

Use a list comprehension:

[y for x,y in A if x>2]

Demo:

>>> A=[(1,'A'),(2,'H'),(3,'K'),(4,'J')]
>>> [y for x,y in A if x>2]
['K', 'J']
>>> 

Answer 2

try :

In [4]: [x[1] for x in A if x[0] > 2]                                                                                                                                                                           
Out[4]: ['K', 'J']

Answer 3

You want to filter based on some condition, then display a representation of those items. There are a few ways to do this.

List comprehension with filtering. This is usually considered idiomatic or “pythonic”

B = [char for char, val in A if val > 2]

Filter and map. This is lazy and useful if your list is very large and you don’t want to hold it all in memory at once.

greater_than_2 = filter(lambda a: a[1] > 2, A)
B = map(lambda a: a[0], greater_than_2)

Or a loop and accumulator. This is good if you have side effects you want to do for each element.

B = []
for char, val in A:
    if val > 2:
        B.append(char)