Մանկական երկաթուղի, լուսանկարի հղումը, Հեղինակ՝ Tigran Kharatyan
(ToDo)
“Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.” - Brian Kernighan
📌 Նկարագիր Մեր առաջին սովորած ֆունկցիան՝ print-ը։ Շատ լավ օրեր ենք անցկացրել իրա հետ, բայց հիմա ժամանակն ա անցնել իրա պռոֆեսինոլ տարբերակին՝ logging-ին։ Սովորում ենք ՝ 1. ոնց նշել logging-ի մակարդակը 2. մեր ուզած ձևով ֆոռմատավորել log-երը 3. գրել log-երը ֆայլի մեջ, ինչպես նաև կոնսոլում 4. json ֆորմատով պահել լոգերը 5. exception-ներ log անել
Հետո անցնում ենք Command Line Interface(CLI)-եր սարքելու գրադարաններին։ CLI-ների շնորհիվ ա որ կարանք գրենք ուղղակի pip install panir ու ինքը գնա ավտոմատ քաշի բերի մեր ուզած գրադարանը, ոչ թե մենք բացենք կոդը որտեղ install հրամանը օգտագործվում ա ու կոդի մեջ նշենք որ արգումենտ որպես մեր գրադարանի անունը գնա։ Սովորում ենք՝ 1. Argparse-ը (ներկառուցված գրադարան) 2. Fire (ֆունկցիաներին CLI-ով դիմելու համար 1-2 տողանոց լուծում) 3. Click (դեկորատորներով աշախտող ուժեղ գրադարն) 4. Typer (FastAPI-ենց գրադարանը type hint-երի վրա հիմնված)
Docs: 1. Doc 2. Logging Cookbook
Videos: 1. Tech With Tim (15 minute video) 2. Corey Schafer, part 1 (14 minute video) 3. Corey Schafer, part 2 (20 minute video)
Ինչի՞ logging
import logging
logging.basicConfig( # Camel case
level=logging.DEBUG,
)
logger = logging.getLogger(__name__)
# Different logging levels
logger.debug("This is a debug message") # 10
logger.info("Application started") # 20
logger.warning("Warning: Potential issue detected") # 30
logger.error("An error occurred") # 40
logger.critical("Critical error!") # 50ERROR:__main__:An error occurred
CRITICAL:__main__:Critical error!import logging
print(logging.INFO)
pi = 3.1420import logging
logging.basicConfig( # Camel case
level=24,
format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
logger = logging.getLogger(__name__)
# Different logging levels
logger.debug("This is a debug message") # 10
logger.info("Application started") # 20
logger.warning("Warning: Potential issue detected") # 30
logger.error("An error occurred") # 40
logger.critical("Critical error!") # 502026-02-18 16:48:02,059 - __main__ - WARNING - Warning: Potential issue detected
2026-02-18 16:48:02,059 - __main__ - ERROR - An error occurred
2026-02-18 16:48:02,060 - __main__ - CRITICAL - Critical error!https://docs.python.org/3/library/logging.html#logrecord-attributes
import logging
logging.basicConfig( # Camel case
level=24,
format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
datefmt='%Y-%m-%d %H:%M:%S'
)
logger = logging.getLogger(__name__)
# Different logging levels
logger.debug("This is a debug message") # 10
logger.info("Application started") # 20
logger.warning("Warning: Potential issue detected") # 30
logger.error("An error occurred") # 40
logger.critical("Critical error!") # 502026-02-18 16:50:18 - __main__ - WARNING - Warning: Potential issue detected
2026-02-18 16:50:18 - __main__ - ERROR - An error occurred
2026-02-18 16:50:18 - __main__ - CRITICAL - Critical error!import logging
logger = logging.getLogger('file_console_logger')
logger.setLevel(logging.DEBUG) # another way to set the level
# Create file handler
file_handler = logging.FileHandler('app.log', mode="a") # a is default
file_handler.setLevel(logging.INFO)
# Create formatter
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
file_handler.setFormatter(formatter)
# Add handlers to logger
logger.addHandler(file_handler)def divide_numbers(a, b):
"""Division with comprehensive logging"""
logger.info(f"Starting division: {a} ÷ {b}")
try:
result = a / b
logger.info(f"Division successful. Result: {result}")
return result
except ZeroDivisionError:
logger.error("Division by zero error!")
return None
except Exception as e:
logger.critical(f"Unexpected error: {e}")
return None
# Test the function
result1 = divide_numbers(10, 3)
result2 = divide_numbers(509, "1")
# Show that logs go to both console and file
print(f"\nResults: {result1}, {result2}")
print("Check 'app.log' file for logged messages")2026-02-18 16:56:49,941 - file_console_logger - INFO - Starting division: 10 ÷ 3
2026-02-18 16:56:49,943 - file_console_logger - INFO - Division successful. Result: 3.3333333333333335
2026-02-18 16:56:49,944 - file_console_logger - INFO - Starting division: 509 ÷ 1
2026-02-18 16:56:49,946 - file_console_logger - CRITICAL - Unexpected error: unsupported operand type(s) for /: 'int' and 'str'
Results: 3.3333333333333335, None
Check 'app.log' file for logged messagesimport logging
logger = logging.getLogger('file_console_logger')
logger.setLevel(logging.DEBUG) # another way to set the level
# Create file handler
file_handler = logging.FileHandler('app.log', mode="a") # a is default
file_handler.setLevel(logging.INFO)
# Create formatter
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
file_handler.setFormatter(formatter)
# Add handlers to logger
logger.addHandler(file_handler)Console handler
# add console handler
console_handler = logging.StreamHandler()
console_handler.setLevel(logging.INFO)
console_handler.setFormatter(formatter) # Use the same formatter
# Add handlers to logger
logger.addHandler(console_handler)# Test the function
result1 = divide_numbers(10, 2)
result2 = divide_numbers(10, 0)
# Show that logs go to both console and file
print(f"\nResults: {result1}, {result2}")
print("Check 'app.log' file for logged messages")2026-02-18 16:59:24,270 - file_console_logger - INFO - Starting division: 10 ÷ 2
2026-02-18 16:59:24,270 - file_console_logger - INFO - Starting division: 10 ÷ 2
2026-02-18 16:59:24,274 - file_console_logger - INFO - Division successful. Result: 5.0
2026-02-18 16:59:24,274 - file_console_logger - INFO - Division successful. Result: 5.0
2026-02-18 16:59:24,278 - file_console_logger - INFO - Starting division: 10 ÷ 0
2026-02-18 16:59:24,278 - file_console_logger - INFO - Starting division: 10 ÷ 0
2026-02-18 16:59:24,284 - file_console_logger - ERROR - Division by zero error!
2026-02-18 16:59:24,284 - file_console_logger - ERROR - Division by zero error!
Results: 5.0, None
Check 'app.log' file for logged messagesimport json
import logging
from datetime import datetime
from logging.handlers import RotatingFileHandler
# Create advanced logger
advanced_logger = logging.getLogger('advanced_app')
advanced_logger.setLevel(logging.DEBUG)
# Rotating file handler
rotating_handler = RotatingFileHandler(
'advanced_app.log',
maxBytes=1024 / 2, # 1/2 KB
backupCount=5
)
rotating_handler.setLevel(logging.INFO)class JSONFormatter(logging.Formatter):
def format(self, record):
log_entry = {
'timestamp': datetime.fromtimestamp(record.created).isoformat(),
'level': record.levelname,
'message': record.getMessage(),
'module': record.module,
'function': record.funcName,
'line': record.lineno
}
return json.dumps(log_entry, ensure_ascii=False)
json_formatter = JSONFormatter()
rotating_handler.setFormatter(json_formatter)
advanced_logger.addHandler(rotating_handler)
# Example class with logging
class Calculator:
def __init__(self):
self.logger = logging.getLogger(f'{__name__}.Calculator')
self.logger.info("Calculator instance created")
def add(self, a, b):
self.logger.debug(f"Adding: {a} + {b}")
result = a + b
self.logger.info(f"Addition result: {result}")
return result
def multiply(self, a, b):
self.logger.debug(f"Multiplying: {a} × {b}")
result = a * b
self.logger.info(f"Multiplication result: {result}")
return result
def divide(self, a, b):
self.logger.debug(f"Dividing: {a} ÷ {b}")
try:
result = a / b
self.logger.info(f"Division result: {result}")
return result
except ZeroDivisionError:
self.logger.error("Division by zero attempted")
return None
for _ in range(509):
# Test the Calculator with logging
calc = Calculator()
calc.add(5, 3)
calc.multiply(4, 7)
calc.divide(10, 2)
calc.divide(10, 0) # This will generate an error log
advanced_logger.info("Calculator operations completed")!uv pip install python-json-loggerUsing Python 3.10.18 environment at: C:\Users\hayk_\.conda\envs\lectures
Audited 1 package in 21ms
import sys
import logging
from pythonjsonlogger import jsonlogger
logger = logging.getLogger(__name__)
stdout_handler = logging.StreamHandler(stream=sys.stdout)
# format with JSON
format_output = jsonlogger.JsonFormatter('%(levelname)s : %(name)s : %(message)s : %(asctime)s')
stdout_handler.setFormatter(format_output)
logger.addHandler(stdout_handler)
logger.error("This is an error message")
logger.critical("This is a critical message"){"levelname": "ERROR", "name": "__main__", "message": "This is an error message", "asctime": "2025-07-20 11:00:44,850"}
{"levelname": "CRITICAL", "name": "__main__", "message": "This is a critical message", "asctime": "2025-07-20 11:00:44,851"}import sys
import logging
from pythonjsonlogger import jsonlogger
logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)
stdout_handler = logging.StreamHandler(stream=sys.stdout)
## Create a file handler
fileHandler = logging.FileHandler("app_with_json.log") # <-
format_output = jsonlogger.JsonFormatter('%(levelname)s : %(name)s : %(message)s : %(asctime)s')
stdout_handler.setFormatter(format_output)
fileHandler.setFormatter(format_output) # <-
logger.addHandler(stdout_handler)
## the file handle handler
logger.addHandler(fileHandler) # <-
logger.error("This is an error message")
logger.critical("This is a critical message"){"levelname": "ERROR", "name": "__main__", "message": "This is an error message", "asctime": "2025-07-20 11:01:06,254"}
{"levelname": "CRITICAL", "name": "__main__", "message": "This is a critical message", "asctime": "2025-07-20 11:01:06,256"}import logging
try:
print(509/0)
except Exception as e:
logging.exception(e)ERROR:root:division by zero
Traceback (most recent call last):
File "C:\Users\hayk_\AppData\Local\Temp\ipykernel_14724\1569123368.py", line 3, in <module>
print(509/0)
ZeroDivisionError: division by zeroԿոդերը՝ 1. Argparse 2. Fire 3. Click 4. Typer
Հղումներ՝ - Argparse docs - Argparse tutorial - Fire GitHub - Typer GitHub - Click docs
| Library | One‑line pitch | Typical use cases | Distinguishing features |
|---|---|---|---|
| Click | Decorator‑driven “Command‑Line Interface Creation Kit” | Production‑grade tools, multi‑command suites | Rich nesting, colors, automatic Bash/Z‑sh completion, context objects; battle‑tested since 2014. (click.palletsprojects.com) |
| Typer | Click‑powered, but driven by type hints | Modern Python ≥ 3.8 projects that already lean on typing | Generates help & shell completion from function signatures; async‑friendly; FastAPI‑style DX. (PyPI) |
| Python Fire | Zero‑boilerplate – expose any Python object with fire.Fire() |
Throw‑away scripts, prototyping, data‑science notebooks | Introspects classes, dicts, even lambdas; perfect for “I just need a CLI around this function”. (GitHub) |