Configuring Python Aliases

In various Linux or macOS environments, the default python command might refer to an older version. To ensure python and pip point to Python 3, aliases can be added to shell configuration files.

For Bash users, append the following to ~/.bashrc:

alias python='/usr/bin/python3'
alias pip='/usr/bin/pip3'

For Zsh users, add these lines to ~/.zshrc:

alias python='/usr/bin/python3'
alias pip='/usr/bin/pip3'

Restart the terminal or source the file to apply changes.

Techniques for Swapping Variables

Exchanging values between two variables is a common task. Python offers several approaches to achieve this.

Using a Temporary Holder

The traditional approach involves a third variable to hold data during the swap.

x = 10
y = 20

holder = x
x = y
y = holder

print(f"x: {x}, y: {y}")

Tuple Unpacking

Python supports a concise syntax for swapping without an intermediate variable by leveraging tuple packing and unpacking.

x = 10
y = 20

x, y = y, x

print(f"x: {x}, y: {y}")

Arithmetic Operations

For numeric values, arithmetic can be used to swap values in place, though this is less common due to potential overflow risks in other languages and readability concerns.

x = 10
y = 20

x = x + y
y = x - y
x = x - y

print(f"x: {x}, y: {y}")

Advanced F-String Formatting

F-strings provide a robust way to embed expressions inside string literals.

Interpolation and Debugging

Variables can be inserted directly. Adding an equals sign = prints the variable name alongside its value, which is excellent for debugging.

status = "active"
count = 42

print(f"Status: {status}")
print(f"{count=}")

Inline Calculations

Mathematical expressions can be evaluated within the curly braces.

total = 100
print(f"Half is {total / 2}")
print(f"{total % 3 = }")

Representation and Formatting

The !r conversion flag calls repr() on the value. Format specifiers allow control over precision.

label = "data"
amount = 12.34567

print(f"Label: {label!r}")
print(f"Amount: {amount:.2f}")

Date Formatting

Datetime objects can be formatted directly within the f-string using format codes.

import datetime

current_time = datetime.datetime.now()
print(f"Today: {current_time:%Y-%m-%d}")

String Formatting Approaches

Aside from f-strings, Python supports the format() method.

F-Strings

username = "Alice"
score = 95
print(f"{username} scored {score}")

The format() Method

This method uses positional or keyword arguments.

username = "Alice"
score = 95
print("{} scored {}".format(username, score))

Understanding Slice Notation

Slicing allows extracting a portion of a sequence. The syntax is [start:stop:step].

• start: The index where the slice begins (inclusive).
• stop: The index where the slice ends (exclusive).
• step: The interval between elements.

numbers = [0, 1, 2, 3, 4, 5]

# Elements from index 1 up to 4
subset = numbers[1:4]  # Result: [1, 2, 3]

# Elements from index 2 to the end
tail = numbers[2:]     # Result: [2, 3, 4, 5]

# Elements from the beginning up to index 3
head = numbers[:3]     # Result: [0, 1, 2]