We've provided some common Python snippets that may be helpful in your development work. Feel free to add any of these Python code examples to your personal Pieces micro repository.
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How to remove Python falsy values
Tags: python, remove falsy, list
Removes Python falsy values from a list by using the filter function.
def remove_falsy(unfiltered_list):
return list(filter(bool, unfiltered_list))
Related links:
- Python code snippet to remove falsy values
- Remove falsy values from a list in Python
How to Flatten a List in Python
Tags: python, list, flatten, recursion
Flattens a nested list using recursion.
def flatten_list(nested_list):
if not(bool(nested_list)):
return nestedList
if isinstance(nested_list[0], list):
return flatten_list(*nested_list[:1]) + flatten_list(nested_list[1:])
return nested_list[:1] + flatten_list(nested_list[1:])
Related links:
- Python Program to Flatten a nested List using Recursion
- Flatten a nested list in Python
How to check for duplicates in a list Python code
Tags: python, list, check duplicates
Using this Python code checks whether a list has duplicate values by using set to grab only unique elements.
def check_for_duplicates(input):
return len(input) != len(set(input))
Related links:
- Python Sets
- Set types in Python
How to check memory usage
Tags: python, memory usage, memory
This snippet in Python checks the total memory an object consumes.
import sys
a = 100;
print(sys.getsizeof(a))
Related links:
- How to check memory usage in Python
- How much of your memory is used by an object in Python
- Use Python to check memory size of an object
How to sort a list of dictionaries in python
Tags: python, dictionaries
Sorts a list of dictionaries in Python.
new_dict = {k: v for k, v in sorted(d.items(), key=lambda item: item[1])}
Related links:
- Sort Python dictionaries by key of value
- Sort dictionary by value in Python
How to merge multiple dictionaries in Python
Tags: python, merge dictionary, dictionary
Merge two python dictionaries into one, or as many dictionaries as you have.
def merge_dicts(*dicts):
super_dict = {}
for dict in dicts:
for k, v in dict.items():
super_dict[k] = v
return super_dict
Related links:
- How to merge dictionaries in Python
- 5 ways to merge dictionaries in Python
How to check if a file exists in Python
Tags: python, file
Checks if a file exists in Python or not.
from os import path
def check_for_file(file_name):
print("File exists: ", path.exists(file_name))
Related links:
- How to check if a file exists or not in Python
- How to check if a file already exists in Python
How to use Python to merge list of lists
Tags: python, file
Merge a series of lists into a list of lists. For example, [1, 2, 3] and [4, 5, 6] would merge into [[1, 2, 3], [4, 5, 6]].
def merge(*args, missing_val = None):
max_length = max([len(lst) for lst in args])
out_list = []
for i in range(max_length):
out_list.append([args[k][i] if i < len(args[k]) else missing_val for k in range(len(args))])
return out_list
Related links:
- Python Snippets you need to know
- Args and Kwargs in Python
How to parse data from a CSV file in Python
Tags: python, csv
Use this Python snippet to parse CSV data and store it in a list of dictionaries.
import csv
def parse_csv_data(csv_path):
csv_mapping_list = []
with open(csv_path) as my_data:
csv_reader = csv.reader(my_data, delimiter=",")
line_count = 0
for line in csv_reader:
if line_count == 0:
header = line
else:
row_dict = {key: value for key, value in zip(header, line)}
csv_mapping_list.append(row_dict)
line_count += 1
Related links:
- Parse CSV data in Python
- How to Parse a CSV File in Python
List Comprehension with Conditionals
Tags: python, list comprehension
Perform different operations in a list comprehension depending on a conditional.
l = [-1, 3, -4, 5, 6, -9]
l = [x if x >= 0 else 0 for x in l]
Related links:
- If else in a list comprehension
- List comprehensions in Python
- When to use list comprehensions in Python
How to write JSON data to file in Python
Tags: python, json, json write
Write data to a JSON file using python.
import json
def write_json_to_file(data, filepath):
with open(filename, "w") as f:
json.dump(data, f, indent=4)
Related links:
- How do I write JSON data to a file
- Use Python to write JSON to a file
How to read data from a JSON file in Python
Tags: python, json, json read
Read JSON data from a file.
import json
def read_json_from_file(filepath):
with open(filepath, "r") as f:
data = json.load(f)
Related links:
- Read JSON file using Python
- Python JSON read write examples
How to create abstract base class in Python
Tags: python, abstract base class, abc
Creates an abstract base class to test if objects adhere to given specifications.
from abc import ABCMeta, abstractmethod
class BaseClass(metaclass=ABCMeta):
@abstractmethod
def foo(self):
pass
@abstractmethod
def bar(self):
pass
class ConcreteClass(BaseClass):
def foo(self):
pass
def bar(self):
pass
instance = ConcreteClass()
Related links:
- Abstract base classes
- Abstract base class Python examples
Creating a thread pool in python
Tags: python, thread pool, threads
Creates a thread pool.
import threading
import time
from queue import Queue
def f(n):
time.sleep(n)
class Worker(threading.Thread):
def __init__(self, queue):
super(Worker, self).__init__()
self.q = queue
self.daemon = True
self.start()
def run(self):
while 1:
f, args, kwargs = self.q.get()
try:
f(*args, **kwargs)
except Exception as e:
print(e)
self.q.task_done()
class ThreadPool(object):
def __init__(self, thread_num=10):
self.q = Queue(thread_num)
for i in range(thread_num):
Worker(self.q)
def add_task(self, f, *args, **kwargs):
self.q.put((f, args, kwargs))
def wait_complete(self):
self.q.join()
if __name__ == '__main__':
start = time.time()
pool = ThreadPool(5)
for i in range(10):
pool.add_task(f, 3)
pool.wait_complete()
end = time.time()
Related links:
- Concurrency in Python - thread pools
- Python thread pool executor example
How to set up a Python virtual environment
Tags: python, virtual environment
Create a virtual environment in Python to manage dependencies.
python -m venv projectnamevenv
Related links:
- How to create a virtual environment in Python
- Python virtual environments a primer
- Why to use virtual environments in Python
Python Singleton decorator
Tags: python, virtual environment, singleton decorator, python singleton
Decorator to create a singleton class.
def singleton(myClass):
instances = {}
def getInstance(*args, **kwargs):
if myClass not in instances:
instances[myClass] = myClass(*args, **kwargs)
return instances[myClass]
return getInstance
@singleton
class TestClass(object):
pass
Related links:
- What is a singleton pattern in Python
- Singleton design pattern in Python
Creating your own data stream in Python
Tags: python, stream
This Python code snippet example creates a stream.
def processor(reader, converter, writer):
while True:
data = reader.read()
if not data:
break
data = converter(data)
writer.write(data)
class Processor:
def __init__(self, reader, writer):
self.reader = reader
self.writer = writer
def process(self):
while True:
data = self.reader.readline()
if not data:
break
data = self.converter(data)
self.writer.write(data)
def converter(data):
assert False, 'converter must be defined'
Related links:
- Data streams in Python
- Python concurrency - Streams
How to do logging in Python
Tags: python, logging
Set logging for debug level along with file name and output to a sample.log file.
import logging
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s:%(name)s:%(message)s')
file_handler = logging.FileHandler('sample.log')
file_handler.setLevel(logging.ERROR)
file_handler.setFormatter(formatter)
stream_handler = logging.StreamHandler()
stream_handler.setFormatter(formatter)
logger.addHandler(file_handler)
logger.addHandler(stream_handler)
Related links:
- How to use logging in Python
- Logging in Python
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