from itertools import groupby
from operator import itemgetter
my_list = [{"a": 1, "b": 2}, {"a": 1, "b": 3}, {"a": 2, "b": 4}]
it = groupby(my_list, key=itemgetter('a'))
result = sum([sum([my_dict['b'] for my_dict in group[1]]) for group in it])
print(result)

from collections import defaultdict
d = defaultdict(list)
d["x"].append(1)
d["y"] = d["x"] + d["z"]
d["x"].append(2)
print(len(d["y"]))

from collections import defaultdict
d = defaultdict(list)
d["x"].append(1)
d["y"] = d["x"] + d["z"]
d["x"].append(2)
print(len(d["y"]))

a = [x for x in range(int(1e5))]
b = (x for x in range(int(1e5)))
x = a.__sizeof__()
y = b.__sizeof__()

a = [x for x in range(int(1e5))]
b = (x for x in range(int(1e5)))
x = a.__sizeof__()
y = b.__sizeof__()

values = ['1', '-3', 'N/A']
def f(val):
    try:
        x = int(val)
        return True
    except ValueError:
        return False
    
vals = list(filter(f, values))
print(vals)

values = ['1', '-3', 'N/A']
def f(val):
    try:
        x = int(val)
        return True
    except ValueError:
        return False
    
vals = list(filter(f, values))
print(vals)

from itertools import compress
x = [1, 2, 3, 4]
y = compress(x, map(lambda i: i & 1, x))
print(*y)

from itertools import compress
x = [1, 2, 3, 4]
y = compress(x, map(lambda i: i & 1, x))
print(*y)

x = {'a' : 1, 'b' : 2, 'c': 3}
y = {t for t in x if t != 'b'}
z = { key:value for key,value in x.items() if key in y }
print(sum(z.values()))