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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Tags: python, remove falsy, list
How to remove Python falsy values
Removes Python falsy values from a list by using the filter function.
def remove_falsy(unfiltered_list):
return list(filter(bool, unfiltered_list))
Tags: python, list, flatten, recursion
How to Flatten a List in Python
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:])
Tags: python, list, check duplicates
How to check for duplicates in a list Python code
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))
Tags: python, memory usage, memory
How to check memory usage
This snippet in Python checks the total memory an object consumes.
import sys
a = 100;
print(sys.getsizeof(a))
Tags: python, dictionaries
How to sort a list of dictionaries in python
Sorts a list of dictionaries in Python.
new_dict = {k: v for k, v in sorted(d.items(), key=lambda item: item[1])}
Tags: python, merge dictionary, dictionary
How to merge multiple dictionaries in Python
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
How to check if a file exists in Python
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))
How to use Python to merge list of lists
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
How to parse data from a CSV file in Python
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
Tags: python, list comprehension
List Comprehension with Conditionals
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]
Tags: python, json, json write
How to write JSON data to file in Python
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)
Tags: python, json, json read
How to read data from a JSON file in Python
Read JSON data from a file.
import json
def read_json_from_file(filepath):
with open(filepath, "r") as f:
data = json.load(f)
Tags: python, abstract base class, abc
How to create abstract base class in Python
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()
Tags: python, thread pool, threads
Creating a thread pool in python
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()
Tags: python, virtual environment
How to set up a Python virtual environment
Create a virtual environment in Python to manage dependencies.
python -m venv projectnamevenv
Tags: python, virtual environment, singleton decorator, python singleton
Python Singleton decorator
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
Creating your own data stream in Python
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'
How to do logging in Python
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)
