J. Carlos Roldán

After so long, I still find basic stuff in Python that I didn't know about. Here are some of my most recent TILs.

1. You can use underscores to separate digits in a number and they'll be ignored by the interpreter:

>>> 1000000  # confusing
1000000
>>> 1e6  # not confusing but creates a float
1000000.0
>>> 1_000_000  # great!
1000000

2. The sum method accepts a second parameter that is the initial value of the sum:

>>> base = 20
>>> sum([1, 2, 3], base)
26

3. With f-strings you can use the = modifier for including the code of the variable interpolation:

>>> a = 1.6
>>> print(f'We have {a=} and {int(a)=}.')
We have a=1.6 and int(a)=1.

4. You can use classes to define decorators instead of functions:

>>> class show_time:
...     def __init__(self, func):
...             self.func = func
...     def __call__(self, *args, **kwargs):
...             start = time()
...             result = self.func(*args, **kwargs)
...             print(f'It took {time() - start:.4f}s')
...             return result
...
>>> @show_time
... def test():
...     return sum(n**2 for n in range(1000000))
...
>>> test()
It took 0.1054s
333332833333500000

5. The mode attribute for open is 'r' by default:

>>> with open('test.txt') as f:
...     print(f.read())
It works!