💡 Python Exam Cheatsheet

A quick review of core Python concepts frequently found in technical assessments and exams. This guide covers list comprehensions, dictionary methods, enumerate, and flexible function arguments.

# Create a list of squares for even numbers from 0 to 9
squares = [x**2 for x in range(10) if x % 2 == 0]
print(squares)

# Output:
# [0, 4, 16, 36, 64]

• List Comprehension: A concise, one-line syntax for creating lists.
• The structure is [expression for item in iterable if condition].
• The if condition part is optional and acts as a filter.

student_scores = {'Alice': 95, 'Bob': 87}

# Safely get a score, providing a default value if the key is missing
charlie_score = student_scores.get('Charlie', 'Not Found')
alice_score = student_scores.get('Alice', 'Not Found')

print(f"Alice: {alice_score}")
print(f"Charlie: {charlie_score}")

# Output:
# Alice: 95
# Charlie: Not Found

• Dictionary .get() Method: Safely access a dictionary key without causing a KeyError.
• The first argument is the key to look up.
• The optional second argument is the default value to return if the key does not exist.

colors = ['red', 'green', 'blue']

for index, value in enumerate(colors):
    print(f"Index: {index}, Value: {value}")

# Output:
# Index: 0, Value: red
# Index: 1, Value: green
# Index: 2, Value: blue

• Using enumerate: The Pythonic way to loop over an iterable when you need both the index and the value.
• It returns a tuple (index, value) for each item in the sequence.

def process_data(*args, **kwargs):
    print(f"Positional args (tuple): {args}")
    print(f"Keyword args (dict): {kwargs}")

process_data(1, 'hello', 3.14, user='admin', status='active')

# Output:
# Positional args (tuple): (1, 'hello', 3.14)
# Keyword args (dict): {'user': 'admin', 'status': 'active'}

• *args: Collects all extra positional arguments into a tuple.
• **kwargs: Collects all extra keyword arguments into a dictionary.
• This pattern allows a function to accept a variable number of arguments.

#Python #PythonExam #Programming #CodeCheatsheet #LearnPython

━━━━━━━━━━━━━━━
By: @DataScience4 ✨