Python Standard Library on Python Beginner Help

datetime.now() Explained

Tue, 09 Jun 2026 00:00:00 +0000

`datetime.now()` Explained

datetime.now() gives you the current local date and time in Python.

Beginners often use it when they want to:

record the current time
print today’s date
create timestamps
work with dates and times in programs

It is important to know that datetime.now() returns a datetime object, not a plain string. That means you can access parts of it like the year, month, day, or hour.

from datetime import datetime

now = datetime.now()
print(now)
print(now.year)
print(now.month)
print(now.day)

Use this when you want the current local date and time as a datetime object.

datetime.strftime() Explained

Tue, 09 Jun 2026 00:00:00 +0000

datetime.strftime() Explained

datetime.strftime() formats a date or time object as a string.

Use it when you want to control how a date or time looks, such as:

2025-04-22
04/22/2025
April 22, 2025
14:30:00

This method is part of Python’s datetime tools. It works with datetime, date, and time objects. If you are new to the module, see the Python datetime module overview.

Quick example #

from datetime import datetime

now = datetime.now()
formatted = now.strftime("%Y-%m-%d %H:%M:%S")
print(formatted)

Example output:

datetime.strptime() Explained

Tue, 09 Jun 2026 00:00:00 +0000

`datetime.strptime()` Explained

datetime.strptime() turns a date or time string into a real datetime object.

This is useful when your date comes from:

user input
a file
a CSV
an API response
a log entry

The important rule is simple:

the text must match the format string exactly

This page focuses on parsing strings into datetime objects. If you want to go the other way and turn a datetime object into text, see datetime.strftime() explained.

json.dump() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

json.dump() Function Explained

json.dump() writes Python data to a file in JSON format.

Use it when you want to save data like dictionaries or lists into a .json file. This is a common way to store settings, API data, or simple structured data.

Quick example #

import json

data = {"name": "Alice", "age": 30}

with open("data.json", "w") as file:
 json.dump(data, file)

Use json.dump() when you want to write Python data directly to a file as JSON.

json.dumps() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

`json.dumps()` Function Explained

json.dumps() converts a Python object into a JSON-formatted string.

Use it when you want JSON as text, not as a file. This is common when sending data to an API, storing JSON in a variable, or printing JSON for debugging.

Quick example #

import json

data = {"name": "Alice", "age": 25}
json_string = json.dumps(data)
print(json_string)

Output:

{"name": "Alice", "age": 25}

Use json.dumps() when you want a JSON string, not a file. It converts Python data like dictionaries and lists into text in JSON format.

json.load() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

`json.load()` Function Explained

json.load() reads JSON data from an open file and converts it into normal Python data.

Use it when your JSON is stored in a file, not in a Python string. This is a common way to load configuration files, saved data, or exported API responses.

Quick answer #

import json

with open("data.json", "r", encoding="utf-8") as file:
 data = json.load(file)

print(data)
print(type(data))

Use json.load() when you already have an open file object. It converts JSON from the file into Python data like dict, list, str, int, float, bool, or None.

json.loads() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

`json.loads()` Function Explained

json.loads() converts JSON text into normal Python data.

Use it when your JSON is already stored in a string, such as:

API response text
JSON copied into a variable
JSON read with file.read()

It is part of Python’s built-in json module.

Quick example #

import json

text = '{"name": "Ana", "age": 20, "is_student": true}'
data = json.loads(text)

print(data)
print(type(data))
print(data["name"])

Output:

{'name': 'Ana', 'age': 20, 'is_student': True}
<class 'dict'>
Ana

Use json.loads() when your JSON is already in a string. It returns normal Python objects like dict, list, str, int, float, bool, and None.

math.ceil() and math.floor() Explained

Tue, 09 Jun 2026 00:00:00 +0000

math.ceil() and math.floor() Explained

math.ceil() and math.floor() are useful when you need to round numbers in a specific direction.

math.ceil() rounds up
math.floor() rounds down

These functions are part of Python’s math module overview, so you must import math before using them.

If you are comparing them with round(), the key difference is simple:

math.ceil() always goes up
math.floor() always goes down
round() goes to the nearest value

Quick example #

import math

print(math.ceil(3.2)) # 4
print(math.floor(3.8)) # 3
print(math.ceil(-3.8)) # -3
print(math.floor(-3.2)) # -4

Use math.ceil() to round up to the next whole number. Use math.floor() to round down to the previous whole number.

math.pow() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

math.pow() Function Explained

math.pow() raises one number to the power of another.

It is part of Python’s math module, so you must import math before using it. This function is useful when you are already working with other math functions, but beginners should also know that math.pow() is different from the ** operator.

Quick answer #

import math

result = math.pow(2, 3)
print(result) # 8.0

math.pow(x, y) returns x raised to the power of y. It always returns a float.

math.sqrt() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

`math.sqrt()` Function Explained

math.sqrt() returns the square root of a number in Python. It is part of the math module, so you need to import that module before using it.

This function is useful when writing formulas, solving geometry problems, or doing basic calculations. On this page, you will learn what math.sqrt() does, what it returns, when to use it, and the most common beginner mistakes.

Quick answer #

import math

result = math.sqrt(25)
print(result) # 5.0

Use math.sqrt() after importing the math module. It returns a float.

os.chdir() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

os.chdir() Function Explained

os.chdir() changes Python’s current working directory.

This matters because the current working directory is the folder Python uses when you give a relative path like "data.txt" or "images/photo.jpg". After you change directories, file operations such as open() will use the new folder.

If you are learning how files and folders work in Python, os.chdir() can be useful. But it can also cause confusion if you are not sure which folder your program is currently using.

os.getcwd() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

os.getcwd() Function Explained

os.getcwd() returns the current working directory in Python.

This is useful when you want to know which folder Python is currently using. It matters because relative file paths are based on this folder. If your code opens or saves files using names like "data.txt", Python will look in the current working directory unless you give a full path.

Quick answer #

import os

current_folder = os.getcwd()
print(current_folder)

Use os.getcwd() to get the current working directory as a string.

os.listdir() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

os.listdir() Function Explained

os.listdir() gives you the names of files and folders inside a directory.

It is a useful function when you want to:

see what is inside a folder
loop through files
build file paths for later work
check directory contents before opening files

Quick example #

import os

items = os.listdir('.')
print(items)

This lists the names of files and folders in the current directory.

What os.listdir() does #

os.listdir() returns the names inside a directory.

os.path.exists() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

os.path.exists() Function Explained

os.path.exists() checks whether a path exists in Python.

You can use it to test:

whether a file exists
whether a folder exists
whether a path is missing

This is useful before you try to open, delete, rename, or work with a path.

Quick example #

import os

path = "example.txt"

if os.path.exists(path):
 print("Path exists")
else:
 print("Path does not exist")

Use this to quickly check whether a file or folder path exists before trying to open or use it.

os.path.join() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

os.path.join() Function Explained

os.path.join() combines file and folder names into a single path string.

Beginners should use it instead of joining path parts by hand because it uses the correct path separator for the current operating system. This helps you avoid mistakes with / and \ when your code runs on different computers.

Quick example #

import os

file_path = os.path.join("data", "reports", "output.txt")
print(file_path)

What this does:

Combines "data", "reports", and "output.txt" into one path
Returns the path as a string
Does not create the file or folder

On one system, the output might look like this:

Python datetime Module Overview

Tue, 09 Jun 2026 00:00:00 +0000

Python datetime Module Overview

The datetime module helps you work with dates, times, and time differences in Python.

It is part of the Python standard library, so you do not need to install anything extra. Beginners often use it to get the current date, create a specific date, format a date as text, or add a number of days to a date.

Quick example #

from datetime import datetime, date, time, timedelta

now = datetime.now()
today = date.today()
meeting = time(14, 30)
one_week = timedelta(days=7)

print(now)
print(today)
print(meeting)
print(now + one_week)

What this code does:

Python json Module Overview

Tue, 09 Jun 2026 00:00:00 +0000

Python json Module Overview

The json module is Python’s built-in tool for working with JSON data.

Use it when you need to:

Read JSON text into Python
Convert Python data into JSON
Work with JSON files
Send or receive structured data in APIs

JSON is one of the most common data formats in programming, so learning the basic json functions is very useful.

Quick example #

import json

person = {"name": "Sam", "age": 25}
json_text = json.dumps(person)
print(json_text)

back_to_dict = json.loads(json_text)
print(back_to_dict["name"])

Output:

Python math Module Overview

Tue, 09 Jun 2026 00:00:00 +0000

Python math Module Overview

The math module is a built-in Python module for common math work.

It gives you extra functions and constants that are not available as basic language features. Beginners often use it for square roots, rounding, powers, and simple numeric calculations.

This page is an overview. It shows what the module is, how to import it, and which parts are most useful to start with.

Quick example #

import math

print(math.sqrt(25))
print(math.ceil(3.2))
print(math.floor(3.8))
print(math.pi)

Expected output:

Python os Module Overview

Tue, 09 Jun 2026 00:00:00 +0000

Python os Module Overview

The os module helps Python work with your operating system. Beginners often use it for files, folders, paths, and environment information.

It is part of Python’s standard library, so you do not need to install anything.

This page is an overview of what os does and when to use it. It is not a full guide to every function in the module.

Quick example #

import os

print(os.getcwd())
print(os.listdir())

This quick example:

Python random Module Overview

Tue, 09 Jun 2026 00:00:00 +0000

Python random Module Overview

The random module is a built-in Python module for working with pseudo-random values.

Beginners often use it to:

generate random numbers
choose a random item from a list
shuffle a list
pick several random items

It is useful for games, simple scripts, testing, and practice programs.

It is not the right tool for passwords, secure tokens, or anything security-related. For that, use the secrets module instead.

Python sys Module Overview

Tue, 09 Jun 2026 00:00:00 +0000

Python sys Module Overview

The sys module is a built-in Python standard library module. It gives you access to information about the Python interpreter and some parts of the program runtime.

Beginners often use sys for:

reading command-line arguments
stopping a program with sys.exit()
checking the Python version
checking the platform
understanding where Python looks for modules

This page is an overview of the most useful parts of sys. It is not a full reference for every attribute in the module.

Python time Module Overview

Tue, 09 Jun 2026 00:00:00 +0000

Python time Module Overview

The time module is a built-in Python module for simple time-related tasks.

Beginners usually use it for:

getting the current timestamp
pausing a program
measuring how long code takes to run

It is a good starting point when you need something simple. If you need readable dates, calendar values, or date math, the datetime module overview is usually a better fit.

Quick example #

import time

print(time.time())
print("Waiting...")
time.sleep(2)
print("Done")

What this does:

random.choice() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

`random.choice()` Function Explained

random.choice() lets you pick one random item from a sequence.

Use it when you want a single random value from something like:

a list
a tuple
a string

It returns the chosen item directly. The sequence must contain at least one item.

import random

colors = ["red", "blue", "green"]
choice = random.choice(colors)
print(choice)

Use random.choice() when you want one random item from a non-empty sequence like a list, tuple, or string.

What `random.choice()` does #

random.choice():

random.randint() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

random.randint() Function Explained

random.randint() gives you a random whole number between two values.

It is part of Python’s random module, so you must import random before using it. A very important detail is that random.randint() includes both the start and end values.

Quick answer #

import random

number = random.randint(1, 10)
print(number)

Use random.randint(start, end) to get a random integer between start and end, including both values.

What random.randint() does #

random.randint():

random.shuffle() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

`random.shuffle()` Function Explained

random.shuffle() puts the items in a list into a random order.

It is important to know two things about this function:

It changes the original list
It returns None

This is a common source of beginner mistakes. If you expect a new list to be returned, your code will not work the way you expect.

Quick example #

import random

numbers = [1, 2, 3, 4, 5]
random.shuffle(numbers)
print(numbers)

Example output:

sys.argv Explained

Tue, 09 Jun 2026 00:00:00 +0000

sys.argv Explained

sys.argv lets a Python script read values passed from the command line.

It is useful for small scripts where you want to give input when you run the file, such as a file name, a word, or a number.

Quick example #

import sys

print(sys.argv)

# Run from terminal:
# python script.py hello 123

sys.argv is a list of command line arguments. The first item is the script name.

sys.exit() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

sys.exit() Function Explained

sys.exit() stops a Python program early.

It is part of the sys module, so you must import sys before using it. This function is common in scripts that need to stop after invalid input, a missing file, or a finished command-line task.

A key detail is that sys.exit() does not simply “shut Python down.” It raises a special exception called SystemExit. That matters because finally blocks still run, and code can catch SystemExit if needed.

sys.path Explained

Tue, 09 Jun 2026 00:00:00 +0000

sys.path Explained

sys.path is one of the most useful things to understand when Python imports are confusing.

It tells Python where to look for modules and packages when you use import. If an import fails, or Python imports the wrong file, sys.path often explains why.

This page shows:

what sys.path is
what it usually contains
how Python uses it during import
how to inspect it safely
when changing it helps, and when it causes more problems

Quick way to inspect `sys.path` #

Use this to see where Python is looking for modules:

time.sleep() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

time.sleep() Function Explained

time.sleep() pauses a Python program for a set amount of time.

It is a simple and useful function for:

adding a delay in a script
building a basic countdown
spacing out repeated output
practicing program flow

This function is part of Python’s time module, so you must import that module before using it.

Quick example #

import time

print("Start")
time.sleep(2)
print("After 2 seconds")

Use time.sleep(seconds) to pause the program. The value can be an integer like 2 or a decimal like 0.5.

time.time() Function Explained

Tue, 09 Jun 2026 00:00:00 +0000

`time.time()` Function Explained

time.time() returns the current time as a number.

In Python, this number is the current Unix timestamp: the number of seconds since January 1, 1970 UTC. Beginners often use it for two simple tasks:

getting the current timestamp
measuring how long some code takes to run

If you want a readable date like 2025-04-22 10:30:00, use the Python datetime module overview instead.

Quick example #

import time

current_timestamp = time.time()
print(current_timestamp)

start = time.time()
time.sleep(1)
end = time.time()
print(end - start)

time.time() returns the current time as seconds since the Unix epoch. It is often used for simple timing.

Python Standard Library on Python Beginner Help

datetime.now() Explained

datetime.now() Explained

datetime.strftime() Explained

datetime.strftime() Explained

Quick example #

datetime.strptime() Explained

datetime.strptime() Explained

json.dump() Function Explained

json.dump() Function Explained

Quick example #

json.dumps() Function Explained

json.dumps() Function Explained

Quick example #

json.load() Function Explained

json.load() Function Explained

Quick answer #

json.loads() Function Explained

json.loads() Function Explained

Quick example #

math.ceil() and math.floor() Explained

math.ceil() and math.floor() Explained

Quick example #

math.pow() Function Explained

math.pow() Function Explained

Quick answer #

math.sqrt() Function Explained

math.sqrt() Function Explained

Quick answer #

os.chdir() Function Explained

os.chdir() Function Explained

os.getcwd() Function Explained

os.getcwd() Function Explained

Quick answer #

os.listdir() Function Explained

os.listdir() Function Explained

Quick example #

What os.listdir() does #

os.path.exists() Function Explained

os.path.exists() Function Explained

Quick example #

os.path.join() Function Explained

os.path.join() Function Explained

Quick example #

Python datetime Module Overview

Python datetime Module Overview

Quick example #

Python json Module Overview

Python json Module Overview

Quick example #

Python math Module Overview

Python math Module Overview

Quick example #

Python os Module Overview

Python os Module Overview

Quick example #

Python random Module Overview

Python random Module Overview

Python sys Module Overview

Python sys Module Overview

Python time Module Overview

Python time Module Overview

Quick example #

random.choice() Function Explained

random.choice() Function Explained

What random.choice() does #

random.randint() Function Explained

random.randint() Function Explained

Quick answer #

What random.randint() does #

random.shuffle() Function Explained

random.shuffle() Function Explained

Quick example #

sys.argv Explained

sys.argv Explained

Quick example #

sys.exit() Function Explained

sys.exit() Function Explained

sys.path Explained

sys.path Explained

`datetime.now()` Explained

`datetime.strptime()` Explained

`json.dumps()` Function Explained

`json.load()` Function Explained

`json.loads()` Function Explained

`math.sqrt()` Function Explained

`random.choice()` Function Explained

What `random.choice()` does #

`random.shuffle()` Function Explained

Quick way to inspect `sys.path` #

`time.time()` Function Explained