10 Python Tips and Tricks for Beginners

Posted by: Zulfikar Akbar Muzakki | in Python | 2 years, 9 months ago | 0 comments

What I love most in Python is its readability and ease of use, which makes Python a good language to start in programming. To make Python learning easier, I will list some useful tips and tricks. Please note that I use Python 3.9 and you must have basic Python knowledge to use it properly.

1. Sorting a list of lists or tuples or dicts

We can use the key parameter in the sort function to provide sorting criteria. We can do this to sort nested lists or tuples based on their last element. If we don't specify a key, it will sort based on the first attribute.

>>> a = [[2, 3, 4], [1, 1, 5], [7, 0, -1]]
>>> sorted(a, key=lambda b: b[-1])
[[7, 0, -1], [2, 3, 4], [1, 1, 5]]

If the list contains a dict, just change the key to key=lambda b: b['some_key']. If we want to reverse the sorting, add reverse=True.

>>> sorted
(a, key=lambda b: b[-1], reverse=True)
[[1, 1, 5], [2, 3, 4], [7, 0, -1]

For more complex sorting, provide a callback as the key

2. Multiple assignment

We can assign multiple values in one line. In the example below, we assign 4 values to 3 variables. But as b has an asterisk in it, it will get values assigned to it as a list.

>>> a, *b, c = 1, 2, 3, 4
>>> a
1
>>> b
[2, 3]
>>> c
4

When the number of values equals the number of variables, it will be stored as a list with one element.

>>> *b = 1
>>> b
[1]

3. Swapping variables

Swapping two variables can be easily done with this trick.

>>> a, b = 1, 2
>>> print(a, b)
1, 2
>>> a, b = b, a
>>> print(a, b)
2, 1

4. Combining strings

We can use str.join() to join list of strings, by providing a string to be used as concatenator. See that the string we provide (' and ') is placed between each element, like between Anna and Bob.

>>> persons = ['Zakki', 'Anna', 'Bob', 'Charlie']
>>> ' and '.join(persons)
'Zakki and Anna and Bob and Charlie'

5. Put variables to string

We could use f-string to put variables to string.

>>> subject = 'Zakki'
>>> object = 'window'
>>> f'{subject} is looking at the {object}'
'Zakki is looking at the window'

6. Merge dictionaries

>>> a = {'a': 1}
>>> b = {'b': 2}
>>> d = {**a, **b, **{'c': 3}}
>>> d
{'a': 1, 'b': 2, 'c': 3}

You can also use this (Python 3.9+ only)

>>> d = a | b | {'c': 3}
>>> d
{'a': 1, 'b': 2, 'c': 3}

7. Map elements

Using this trick we can map an element in one list or tuple to another list or tuple

>>> a = [1, 2, 3]
>>> b = ['a', 'b', 'c']
>>> list(zip(a, b))
[(1, 'a'), (2, 'b'), (3, 'c')]
>>> list(zip(b, a))
[('a', 1), ('b', 2), ('c', 3)]

8. Ternary operator

Use simple this one line ternary operator with syntax value_when_true if condition else value_when_false

>>> a = 'Big'
>>> b = 'Small' if a == 'Big' else 'Big'
>>> b
>>> 'Small'

Instead of

if a == 'Big':
    b = 'Small'
else:
    b = 'Big'

9. Removing duplicates

By converting to set, we get the unique values.

>>> a = [1, 1, 2, 2, 3]
>>> a
[1, 1, 2, 2, 3]
>>> list(set(a))
[1, 2, 3]

10. Find elements showing in both lists

We can do that by converting to set, then use set.intersection()

>>> a = [1, 2, 3]
>>> b = [1, 2]
>>> set_a = set(a)
>>> set_b = set(b)
>>> set_a.intersection(set_b)
{1, 2}

I hope this article helps you in many ways.

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