Not understanding the use of {0:25} and {1:3}

[yang19177]

I was working through a book on machine learning and came across this snippet of code.

import mglearn import matplotlib.pyplot as plt import numpy as np import pandas as pd from sklearn.datasets import fetch_lfw_people people = fetch_lfw_people(min_faces_per_person=20, resize = 0.7) image_shape = people.images[0].shape counts = np.bincount(people.target) for i, (count,name) in enumerate(zip(counts, people.target_names)): print("{0:25} {1:3}".format(name, count), end=' ') if (i+1)% 3 == 0: print()

I'm not sure what is the use of {0:25} and {1:3} in the second last print function. I have not seen this before.
Thanks.

[snippsat]

I'm not sure what is the use of {0:25} and {1:3} in the second last print function

It's string formatting and the older version .format() that was new in Python 2.6.

name = 'Python forum' count = 10 >>> print("{0:25} {1:3}".format(name, count), end=' ') Python forum 10 

With new f-string format new in Python 3.6,this is what you should use now.

>>> print(f"{name:25}{count:3}", end=' ') Python forum 10 

So eg it's padding and aligning of strings,can play around with <>^

>>> print(f"{name:>14}{count:^20}") Python forum 10 >>> print(f"{name:>20}{count:^5}") Python forum 10 >>> print(f"{name:>20}{count:<5}") Python forum10 >>> for word in 'f-strings are cool'.split(): ... print(f'{word.upper():~^20}') ... ~~~~~F-STRINGS~~~~~~ ~~~~~~~~ARE~~~~~~~~~ ~~~~~~~~COOL~~~~~~~~