Lists & loops
Iterate, transform, and combine sequences with readable loop patterns.
Enumerate a Python List with a Custom Start Index
Iterate over a list with an index that starts at a custom value (like 5) using Python's built-in enumerate() function with the start parameter.
fruits = ["apple", "banana", "cherry", "date"]
for index, fruit in enumerate(fruits, start=5):
print(f"{index}: {fruit}")Find All Occurrences of an Item in a Python List
Loop through a list with enumerate() to collect the index of every match for a target value.
def find_all(data, target):
"""Return indices of every occurrence of target in a list."""
indices = []
for index, item in enumerate(data):
if item == target:
indices.append(index)
return indices
if __name__ == "__main__":
sample = [10, 20, 30, 20, 40, 20, 50]
target_value …Format Lists of Tuples into Numbered Lines in Python
This code loops through a list of (name, grade) tuples and formats each into a numbered line using enumerate and f-strings.
def format_students(students):
formatted = []
for i, student in enumerate(students, start=1):
name, grade = student
formatted.append(f"{i}. {name}: {grade}")
return "\n".join(formatted)
if __name__ == "__main__":
students = [
("Alice", 92),
("Bob", 85),
("Charl…How to Process Text Lines with Lists and Loops in Python
This code processes a list of text lines by stripping whitespace, converting to uppercase, and reporting character counts per line and totals.
def process_text(lines):
"""Convert a list of text lines to uppercase and report line statistics."""
processed = []
total_chars = 0
for index, line in enumerate(lines, start=1):
cleaned = line.strip().upper()
processed.append(cleaned)
total_chars += len(cleaned)
pri…How to Process Text with Lists and Loops in Python
A beginner-friendly text processor that splits a sentence into words, filters by length, counts vowels, and reports results using lists and loops.
text = "Python makes text processing easy and fun"
words = text.lower().split()
print("Words in the sentence:")
for index, word in enumerate(words, start=1):
print(f"{index}. {word}")
filtered_words = [word for word in words if len(word) > 3]
print(f"\nWords longer than 3 characters: {filtered_words}")
letter…How to Process Text with Lists and Loops in Python
Iterate over a list of text lines to count words, show uppercase versions, and report character counts per line.
# text_processor.py
def process_text(lines):
"""Count words, show uppercase, and count characters per line."""
total_words = 0
print("Line-by-line analysis:")
for i, line in enumerate(lines, start=1):
words = line.split()
total_words += len(words)
print(f" Line {i}: {len(words…How to check list items by type and emptiness in Python
Loop through a list with enumerate(), classify each item as empty, number, or text, and print a formatted status for each element.
def check_data(data):
"""Check each item in a list and print whether it's valid."""
for i, item in enumerate(data):
if item is None or item == "":
status = "empty"
elif isinstance(item, (int, float)):
status = "number"
else:
status = "text"
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Lists & loops — Python code examples
What you will find here
This page collects lists & loops snippets — short, copy-ready Python you can paste into our free online IDE and run without installing anything. Each sample includes a plain-English explanation and the full source code.
Samples vs tutorials and challenges
Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.