Lists & loops
Iterate, transform, and combine sequences with readable loop patterns.
Extract Data by Type from a List in Python: Numbers and Strings
Loop through a mixed list to filter out numeric and string values into separate lists.
def extract_numbers(items):
"""Extract all numeric values from a mixed list."""
numbers = []
for item in items:
if isinstance(item, (int, float)) and not isinstance(item, bool):
numbers.append(item)
return numbers
def extract_strings(items):
"""Extract all string values from a…How to Convert Data Types in Python Lists
Convert a mixed list of values to integers, floats, or strings based on their content, with graceful fallback for unparseable strings.
def convert_data(data):
"""Convert a mixed list of values to strings, ints, and floats."""
result = []
for item in data:
if isinstance(item, (int, float)):
result.append(str(item))
elif isinstance(item, str):
try:
if '.' in item:
r…How to Filter None Values from a Mixed List in Python
Filter None values from a mixed Python list using a list comprehension with the `is not None` condition.
mixed_list = [1, None, "hello", None, 3.14, None, [1, 2], None]
filtered_list = [item for item in mixed_list if item is not None]
print(f"Original list: {mixed_list}")
print(f"Filtered list: {filtered_list}")
print(f"Original length: {len(mixed_list)}, Filtered length: {len(filtered_list)}")How to Filter a List in Python with a Loop
Filter a list of numbers by a threshold using a for loop and append results to a new list, then print the filtered values and count.
ages = [34, 12, 45, 8, 67, 21, 18, 55, 3]
threshold = 18
adults = []
for age in ages:
if age >= threshold:
adults.append(age)
print("All ages:", ages)
print("Adults (18+):", adults)
print("Count of adults:", len(adults))How to Get the Union of Two Lists Without Duplicates in Python
Merge two lists and remove duplicate values using a set, then convert back to a list.
def union_without_duplicates(list1, list2):
return list(set(list1 + list2))
if __name__ == "__main__":
list_a = [1, 2, 3, 4]
list_b = [3, 4, 5, 6]
result = union_without_duplicates(list_a, list_b)
print(f"Union of {list_a} and {list_b}: {result}")How to Normalize a List of Numbers in Python
This Python function normalizes a list of numeric values to the range [0, 1] using min-max scaling, returning a new list and leaving the original unchanged.
def normalize(data):
"""
Normalize a list of numeric values to the range [0, 1].
Returns a new list, leaving the original unchanged.
"""
if not data:
return []
min_val = min(data)
max_val = max(data)
# Handle the edge case where all values are identical
if min_val …How to Safely Convert a List of Strings to Integers in Python
Convert a list of strings to integers while skipping invalid entries and collecting the failed values for inspection.
def safe_to_int(values):
"""Safely convert a list of strings to integers, skipping invalid entries."""
result = []
errors = []
for value in values:
try:
result.append(int(value))
except (ValueError, TypeError):
errors.append(value)
return result, errors
if …Replace Negative Values in a List with Python
This code defines a function that replaces every negative number in a list with a replacement value, defaulting to zero, using a list comprehension.
def replace_if_negative(values, replacement=0):
return [replacement if value < 0 else value for value in values]
if __name__ == "__main__":
numbers = [5, -3, 8, -1, 0, -7, 2]
result = replace_if_negative(numbers)
print(f"Original: {numbers}")
print(f"Replaced: {result}")Browse by section
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Lists & loops — Python code examples
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