tak co koukám vyplatí se slučování (tedy ten prostřední příklad...):
import time
a = time.time()
for i in range(0, 999999):
array = ['a','b','b','d']
array2 = [" {} ".format(x) for x in array]
b = time.time()
c = b - a
print c
a = time.time()
for i in range(0, 999999):
array = ['a','b','b','d']
array2 = [" "+x+" " for x in array]
b = time.time()
c = b - a
print c
a = time.time()
for i in range(0, 999999):
array = ['a','b','b','d']
array2 = map(lambda x: " "+x+" ", array)
b = time.time()
c = b - a
print c
ondrej@ondrej:~$ python /mnt/data/time.py
1.14769887924
0.774380922318
1.0320391655