List Comprehension

Looking at the below code, write down the final values of A0, A1, …An.

A0 = dict(zip(('a','b','c','d','e'),(1,2,3,4,5)))
A1 = range(10)
A2 = sorted([i for i in A1 if i in A0])
A3 = sorted([A0[s] for s in A0])
A4 = [i for i in A1 if i in A3]
A5 = {i:i*i for i in A1}
A6 = [[i,i*i] for i in A1]

Link: problem source.

The trap of lists = [[]] * 5:

>>> lists = [[]] * 5
>>> lists
[[], [], [], [], []]
>>> lists[0].append(1)
>>> lists
[[1], [1], [1], [1], [1]]
>>> id(lists[2])
139762852067080
>>> id(lists[3])
139762852067080

TODO: what’s the root cause?

Print Function

Print with specific number of digits:

print("{:2d}".format(1))
>>> _1
print("{:02d}".format(1))
>>> 01
print("{:02d}".format(1100))
>>> 1100
print("{:.2f}".format(1.5))
>>> 1.50

Relative Import Path

TODO: why and how to solve it?

Link: stackoverflow explanation.