Сергей

Реализаций можно написать много.

Вариант 1: google "python split list into chunks"

Вариант 2: если в проекте используется numpy:

import numpy as np

def split(seq, num_chunks):
    lst = np.array_split(np.array(seq), num_chunks)
    return [x.tolist() for x in lst if len(x)]

Вариант 3 (только сейчас придумал, для py 2):

from __future__ import division
import math

def split(seq, num_chunks):
    assert num_chunks
    pos = 0
    sz = len(seq)
    result = []
    while pos < sz:
        num_items = int(math.ceil((sz - pos) / num_chunks))
        result.append(seq[pos:pos + num_items])
        pos = pos + num_items
        num_chunks -= 1
    return result

split([1, 2, 3, 4, 5, 6, 7, 8, 9], X)

# X
# 1   [[1, 2, 3, 4, 5, 6, 7, 8, 9]]
# 2   [[1, 2, 3, 4, 5], [6, 7, 8, 9]]
# 3   [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
# 4   [[1, 2, 3], [4, 5], [6, 7], [8, 9]]
# 5   [[1, 2], [3, 4], [5, 6], [7, 8], [9]]
# 6   [[1, 2], [3, 4], [5, 6], [7], [8], [9]]
# 7   [[1, 2], [3, 4], [5], [6], [7], [8], [9]]
# 8   [[1, 2], [3], [4], [5], [6], [7], [8], [9]]
# 9   [[1], [2], [3], [4], [5], [6], [7], [8], [9]]
# 10  [[1], [2], [3], [4], [5], [6], [7], [8], [9]]

Вариант 4 - вариация варианта 3. Теперь split это генератор и всегда возвращает указанное кол-во частей/отрезков

def split(seq, num_chunks):
    assert num_chunks
    pos = 0
    sz = len(seq)
    while pos < sz:
        num_items = int(math.ceil((sz - pos) / num_chunks))
        yield seq[pos:pos + num_items]
        pos = pos + num_items
        num_chunks -= 1

    for _ in range(num_chunks):
        yield []

list(split([1, 2, 3, 4, 5, 6, 7, 8, 9], X))

# X
# ...
# 9   [[1], [2], [3], [4], [5], [6], [7], [8], [9]]
# 10  [[1], [2], [3], [4], [5], [6], [7], [8], [9], []]
# 11  [[1], [2], [3], [4], [5], [6], [7], [8], [9], [], []]

и т. д.

В Вашем случае лямбда-функции не особо нужны, есть варианты короче и быстрее:

df['col3'] = df.min(axis=1)
# или
import numpy as np
df['col3'] = np.minimum(df.col1, df.col2)

Самый простой, наверное, multiprocessing и Queue.
https://docs.python.org/3.6/library/multiprocessin...