👩‍💻 { A JavaScript developer, who try to solves LeetCode problems using Python and Java )

My Python knowledge feels like a puzzle with missing pieces🤔
because I’ve learned the language primarily through code samples & solving problems.

I’m working on filling in the gaps and deepening my understanding of the language by writing TIL.

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Solved Problems 📝

• 659. Encode and Decode Strings - my solution

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Key Learnings 🤔

• String Interpolation in Python
• Python List Slicing in Practice

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String Interpolation in Python

In Python, you can't connect different types directly, as Python does not perform implicit type coercion like JavaScript. There is a different Ways to Perform String Interpolation.

f-String (Python 3.6+)

The closest equivalent to JavaScript template literals, with support for:

• Embedded expressions
• Multi-line formatting

num1 = 2
num2 = 3
result = f"The sum of {num1} and {num2} is {num1 + num2}."
print(result)  # Output: The sum of 2 and 3 is 5.

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str.format()

Uses placeholders {} replaced by arguments passed to the format() method.

name = "Bob"
age = 25

greeting = "Hello, {}! You are {} years old.".format(name, age)
print(greeting)  # Output: Hello, Bob! You are 25 years old.

keyword_greeting = "Hello, {name}! You are {age} years old.".format(name="Charlie", age=40)
print(keyword_greeting)  # Output: Hello, Charlie! You are 40 years old.

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% Operator

An older style resembling the syntax of C's printf.

name = "Dave"
age = 35
greeting = "Hello, %s! You are %d years old." % (name, age)
print(greeting)  # Output: Hello, Dave! You are 35 years old.

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Template Strings

The string module provides a Template class for simple substitutions.

from string import Template

name = "Eve"
age = 28
template = Template("Hello, $name! You are $age years old.")
greeting = template.substitute(name=name, age=age)
print(greeting)  # Output: Hello, Eve! You are 28 years old.

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Python List Slicing in Practice

List slicing allows flexible operations on lists, even supporting "out-of-bound" indexing without raising errors.

Shallow Copy

arr = [1, 2, 3]
copy_arr = arr[:]
print(copy_arr)  # Output: [1, 2, 3]

Subset Assignment

arr = [1, 2, 3, 4, 5]
arr[1:4] = [9, 8, 7]
print(arr)  # Output: [1, 9, 8, 7, 5]

Clearing a List

arr = [1, 2, 3]
arr[:] = []
print(arr)  # Output: []

Step Manipulations

arr = [0, 1, 2, 3, 4, 5, 6]

# Every second element
print(arr[::2])  # Output: [0, 2, 4, 6]

# Every second element, reversed
print(arr[::-2])  # Output: [6, 4, 2, 0]

# From index 1 to 7, every second element
print(arr[1:7:2])  # Output: [1, 3, 5]

# From index 6 to 0, reversed, every second element
print(arr[6:0:-2])  # Output: [6, 4, 2]

Multidimensional Arrays

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

# First row
print(matrix[0])  # Output: [1, 2, 3]

# First column
print([row[0] for row in matrix])  # Output: [1, 4, 7]

# Submatrix
print(matrix[1:3])  # Output: [[4, 5, 6], [7, 8, 9]]

Combining Slicing with List Comprehensions

arr = [1, 2, 3, 4, 5]

# Reverse and double elements
print([x * 2 for x in arr[::-1]])  # Output: [10, 8, 6, 4, 2]

Using Negative Indices

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

# From index -2 to end
print(a[-2:])  # Output: [8, 9]

# From start to index -3 (excluding -3)
print(a[:-3])  # Output: [1, 2, 3, 4, 5, 6]

# From index -4 to -1 (excluding -1)
print(a[-4:-1])  # Output: [6, 7, 8]

# From index -8 to -1, every second element
print(a[-8:-1:2])  # Output: [2, 4, 6, 8]