Cool Python tricks you are not using, but you should.

Cool Python tricks you are not using, but you should.

Ternary operator

ans = z if a > b else c

is same as

if a > b:
    ans = z
else:
    ans = c

Short circuit

result = counter or 15

is same as

result = counter if counter else 15

is same as

if not counter:
    result = 15
else:
    result = counter

Comparison

if 3 > a > 1 < b < 5: foo()

instead of

if a > 1 and b > 1 and  a < 3 and  b < 5: foo()

Reverse an iterable

[1, 2, 3, 4][::-1] # => [4, 3, 2, 1]

Unpacking

z = [1, 2, 3, 4, 5, 6]
a, *b, c = z

is same as

b = []
for i, val in enumerate(z):
    if i == 0:
        a = val
    elif i == len(z) - 1:
        c = val
    else:
        b.append(val)

swapping two variables

a, b = b, a
# this is tuple unpacking

Last element of an iterable

To fetch the last element of any iterable like list, tuple or set.

For list/tuple

>>> zlst = ['a', 'b', 'c']
>>> zlst[-1]
'c'
>>> *_, e = zlst
# if you do not want to use the non-last elements
>>> e
'c'
>>> ztup = ('a', 'b', 'c')
>>> ztup[-1]
'c'

For set

>>> my_set = {'a', 'b', 'c'}
>>> my_set[-1]
TypeError: 'set' object is not subscriptable
>>> q, w, e = my_set
>>> e
'c'
>>> *q, e = my_set
>>> e
'c'
>>> q
['a', 'b']
# q is not a set

More tricks will be added soon. The cover picture is copyrighted to the author.

Code formatting

  • Use black to format your codebase.
  • Have a large project, can do one at a time or one file at a time.
  • Here is my favorite config I use to auto-format my code modules.
$ pip install black
$ black folder/file.py -l 120 -t py38 
reformatted folder/file.py
All done! ✨ 🍰 ✨
1 file reformatted.
  • -l: I use 120 as the maximum characters I accept in a line
  • -t py38: Python 3.8 specific custom formatting.

Further reading