Joshua Rosato
Joshua Rosato

Joshua Rosato

Python Tricks

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Joshua Rosato
·Jun 26, 2022·

5 min read

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Here are some cool Python tricks you may not know about.

I believe that it's easiest to learn by example, so I won't be explaining something unless the example itself isn't explanatory enough. Let me know if in future you'd prefer a more in-depth explanation.

If you'd like to see more tricks in Python, JavaScript, or any other language, please let me know!

And without further ado, let's begin!

Swap the Value of Two Variables

a = 3
b = 4
print(f"A is currently {a} and B is currently {b}.")
# => A is currently 3 and B is currently 4.

# Now let's swap the variables.
a, b = b, a
print(f"A is currently {a} and B is currently {b}.")
# => A is currently 4 and B is currently 3.

You can also enclose the values in parentheses, which I find a little nicer.

a = 3
b = 4
(a, b) = (b, a)
print(f"A is currently {a} and B is currently {b}.")
# => A is currently 4 and B is currently 3.

Or in square brackets, if you prefer.

a = 3
b = 4
[a, b] = [b, a]
print(f"A is currently {a} and B is currently {b}.")
# => A is currently 4 and B is currently 3.

Find the Smallest and Largest Values in a List

my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

smallest = min(list)
largest = max(list)

print(f"The smallest value in the list is {smallest}, and the largest value in the list is {largest}.")

# => The smallest value in the list is 1, and the largest value in the list is 10.

List Comprehensions

squares = [x**2 for x in range(20)]

# => [0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 256, 289, 324, 361]

oddCubes = [x**3 for x in range(20) if x % 2 != 0]

# => [1, 27, 125, 343, 729, 1331, 2197, 3375, 4913, 6859]

This would be equivalent to the following code, which uses a more traditional imperative approach.

squares = []
for x in range(20):
    squares.append(x**2)

oddCubes = []
for x in range(20):
    if x % 2 != 0:
        oddCubes.append(x**3)

Remove Duplicates from a List

An easy way to remove duplicate values from a list is to convert the list to a set, and then back again. Sets are unordered data structures that don't allow duplicates.

dupe_list = [1, 2, 3, 1, 2, 3, 4, 5, 6, 4, 5, 6, 7, 7, 7]
clean_list = list(set(dupe_list))
print(clean_list)
# => [1, 2, 3, 4, 5, 6, 7]

It's worth noting for larger lists that this method isn't the most efficient.

Reversing a List

The reversed function produces a list_reverseiterator object, which you can then convert into a list. Note that this doesn't modify the original list.

ord_list = [1, 2, 3, 4, 5]
rev_list = list(reversed(ord_list))

You can also reverse a list using a slice.

This syntax slices the entire list, but using a step of -1, which causes the list to be returned in reverse order.

Once again, this doesn't modify the original list, so you'll need to save it in a variable.

ord_list = [1, 2, 3, 4, 5]
rev_list = ord_list[::-1]

Using the reverse method on a list will change it in place.

ord_list = [1, 2, 3, 4, 5]
ord_list.reverse()
print(ord_list)
# => [5, 4, 3, 2, 1]

Use Lambdas for Small Functions

# Instead of having to type out an entire function definition, such as the below:
def sum(x, y):
    return x + y

# We can use lambda functions to make this quicker and easier:
sum = lambda x, y: x + y

sum(3, 4)
# => 7

Python doesn't support multi-line lambdas, so this trick is only good for simple functions.

Ternary Operator

Python supports the ternary operator using the below syntax.

a = 3
b = 4

max = a if a > b else b
min = a if a < b else b

print(f"The min is {min} and the max is {max}.")
# => The min is 3 and the max is 4.

Combining Dictionaries

a = { 1: "a", 2: "b", 3: "c" }
b = { "d": 4, "e": 5, "f": 6 }

c = {**a, **b}
print(c)
# => { 1: 'a', 2: 'b', 3: 'c', 'd': 4, 'e': 5, 'f': 6 }

Formatting Big Integers

Python allows you to use underscores within integer numbers to make reading them easier.

hundred_thousand = 100_000
million = 1_000_000
ten_million = 10_000_000
hundred_million = 100_000_000
billion = 1_000_000_000

DivMod

I wanted to share this one as I doubt many people know about it.

divmod is a cool little function that returns a tuple containing both the quotient and remainder of a division.

divmod(7, 2)
# => (3, 1)
# Explanation: 2 goes into 7 a total of 3 times, with a remainder of 1.

# Without divmod, you'd have to perform 2 separate operations to get both numbers.
7 // 2 # Floor division to get the quotient.
7 % 2 # Modulus to get the remainder.

Once again, if you'd like to see more tricks in Python, JavaScript, or any other language, please let me know!

Thanks for reading!

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