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How to Count Occurrences of a Value in a Python List
Counts how many times a specific value appears in a list using a simple loop and a counter variable.
def count_occurrences(data, target):
count = 0
for item in data:
if item == target:
count += 1
return count
if __name__ == "__main__":
numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
target_value = 5
result = count_occurrences(numbers, target_value)
print(f"The value {targ…How to Count, Double, and Find Max in a Python List
Three beginner-friendly Python functions that count even numbers, double each value, and find the maximum in a list using simple loops.
def count_even_numbers(numbers):
"""Return the count of even numbers in a list."""
count = 0
for num in numbers:
if num % 2 == 0:
count += 1
return count
def double_values(numbers):
"""Return a new list with each value doubled."""
doubled = []
for num in numbers:
…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 Find the Mode in a Python List
Find the most frequent value (mode) in a Python list using the collections.Counter class, handling empty lists and ties.
from collections import Counter
def find_mode(numbers):
if not numbers:
return None
counts = Counter(numbers)
max_count = max(counts.values())
modes = [num for num, count in counts.items() if count == max_count]
return modes[0] if len(modes) == 1 else modes
if __name__ == "__main__":
…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 Summarize a List of Numbers in Python
Loop over a list of numbers to compute total, count, average, min, and max, then return them in a dictionary.
def summarize_numbers(numbers):
"""Return a dict with basic stats for a list of numbers."""
total = 0
count = 0
smallest = numbers[0]
largest = numbers[0]
for num in numbers:
total += num
count += 1
if num < smallest:
smallest = num
if num > largest:…How to summarize and transform lists in Python
Compute count, sum, min, max, and average for a list and multiply each element by a factor using simple loops and built-in functions.
def summarize(data):
"""Return a summary of a list: count, sum, min, max, average."""
count = len(data)
total = sum(data)
minimum = min(data)
maximum = max(data)
average = total / count if count else 0
return count, total, minimum, maximum, average
def multiply_elements(data, factor=2):
…Truncate List Keeping Last N Elements in Python
Return a new list containing only the last N elements from a sequence, handling edge cases like zero or oversized counts.
def truncate(seq, keep_last_n):
"""Return a new list keeping only the last n elements."""
if keep_last_n <= 0:
return []
return list(seq)[-keep_last_n:]
if __name__ == "__main__":
data = [10, 20, 30, 40, 50, 60]
print(truncate(data, 3))
print(truncate(data, 0))
print(truncate(data…How to Count Items with Default Parameters in Python
Define a Python function that prints each item with a running counter, using default parameters to allow custom start values and step increments.
def count_items(items, start=0, step=1):
"""Count items in a list with configurable start value and step."""
count = start
for item in items:
print(f"{count}: {item}")
count += step
if __name__ == "__main__":
fruits = ["apple", "banana", "cherry"]
print("Default parameters (start=0…How to Create a Counter Closure in Python
Build a closure in Python that remembers and increments a counter across calls without using global variables.
def create_counter(start=0):
count = start
def increment():
nonlocal count
count += 1
return count
return increment
if __name__ == "__main__":
counter = create_counter(10)
print(counter())
print(counter())
print(counter())How to Create a Timing Decorator in Python
A Python decorator that measures and prints the execution time of any function using time.perf_counter.
import time
from functools import wraps
def timing_decorator(func):
@wraps(func)
def wrapper(*args, **kwargs):
start = time.perf_counter()
result = func(*args, **kwargs)
end = time.perf_counter()
elapsed = end - start
print(f"{func.__name__} took {elapsed:.6f} seconds"…How to Create an Iterator Class with Dunder Methods in Python
A minimal Counter class implementing __iter__ and __next__ to act as a self-iterating iterator, yielding numbers from start to end-1.
class Counter:
def __init__(self, start=0, end=5):
self.current = start
self.end = end
def __iter__(self):
return self
def __next__(self):
if self.current >= self.end:
raise StopIteration
value = self.current
self.current += 1
return val…Count Files by Extension in Python
Count files in a directory grouped by file extension using Python's standard library.
from pathlib import Path
def count_files_by_extension(directory: str) -> dict[str, int]:
"""Count files in a directory grouped by file extension."""
data = {}
for path in Path(directory).iterdir():
if path.is_file():
ext = path.suffix.lower() or "(no extension)"
data[ext] =…How to Extract IP Address Counts from Access Logs in Python
Read a web server access log, count occurrences of each IP address using regex and Counter, and print the ranked results.
import re
from collections import Counter
from pathlib import Path
def extract_ip_counts(log_file_path):
ip_pattern = r'^(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})'
ip_counter = Counter()
with open(log_file_path, 'r') as file:
for line in file:
match = re.match(ip_pattern, line)
…How to Find Files by Extension in Python
This code walks a directory tree with pathlib, collects all file paths, and counts them by extension to summarize a project's contents.
from pathlib import Path
def get_project_files(base_path="."):
"""Return a sorted list of all file paths under base_path."""
base = Path(base_path)
files = [p for p in base.rglob("*") if p.is_file()]
return sorted(files)
def count_by_extension(files):
"""Return a dict mapping extension (lowercase…How to check file data in Python
Check if a file exists and is a regular file, then return its name, size, line count, and first line.
def check_file_data(file_path):
from pathlib import Path
path = Path(file_path)
if not path.exists():
return f"File '{file_path}' does not exist."
if not path.is_file():
return f"'{file_path}' is not a regular file."
size = path.stat().st_size
lines = path.read_text(encodin…Build a defaultdict histogram of categories in Python
Count occurrences of each category in a list using collections.defaultdict(int) for automatic initialization.
from collections import defaultdict
def build_category_histogram(items):
"""Count occurrences of each category in a list of items."""
histogram = defaultdict(int)
for item in items:
histogram[item] += 1
return dict(histogram)
if __name__ == "__main__":
categories = ["fruit", "vegetable", …Count Word Frequency in Python with dict
Count how often each word appears in a text using Python's collections.Counter and regular expressions.
from collections import Counter
import re
def count_word_frequency(text):
"""Count frequency of each word in text (case-insensitive)."""
words = re.findall(r"\b\w+\b", text.lower())
return dict(Counter(words))
if __name__ == "__main__":
sample_text = "The quick brown fox jumps over the lazy dog. The …Count Words in Python with Dictionaries and Sets
Text analysis example that counts total words, finds unique words with a set, and tallies character frequencies with a dictionary.
def analyze_text(text: str) -> dict:
"""Count words, find unique words, and show common characters."""
words = text.lower().split()
word_count = len(words)
unique_words = set(words)
char_counts = {}
for word in words:
for char in word:
if char.isalpha():
…Count word frequency in Python with dict and Counter
Count how often each word appears in a string using Counter, converted to a plain dict, and print results alphabetically.
from collections import Counter
import re
def count_word_frequency(text):
words = re.findall(r'\b\w+\b', text.lower())
return dict(Counter(words))
if __name__ == "__main__":
sample_text = "The quick brown fox jumps over the lazy dog. The dog barks, and the fox runs."
frequency = count_word_frequency(…How to Convert a Counter to a Plain Dict with Sorted Items in Python
This code converts a collections.Counter into a regular dictionary with items sorted by key, useful for stable, readable output.
from collections import Counter
def counter_to_sorted_dict(counter):
"""Convert a Counter to a plain dict with sorted items."""
return dict(sorted(counter.items()))
if __name__ == "__main__":
# Example usage
data = Counter(['apple', 'banana', 'apple', 'cherry', 'banana', 'date', 'apple'])
print("…How to Count Co-occurrence Pairs in Python with Nested Dictionaries
This code counts how often any two items appear together in the same group, using a nested defaultdict keyed by item pairs.
from itertools import combinations
from collections import defaultdict
def count_cooccurrences(items_per_group):
cooccurrence = defaultdict(lambda: defaultdict(int))
for group in items_per_group:
for a, b in combinations(sorted(group), 2):
cooccurrence[a][b] += 1
cooccurrence[b…Browse by section
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