Python) Module and package

The module is a file that consists of functions, variables, and classes. Modules in Python are considered code libraries in other languages. 

The built-in functions are the parts of the Python standard module. Click the link to see the built-in functions. 

2. Built-in Functions — Python 3.6.15 documentation

2. Built-in Functions — Python 3.6.15 documentation

You must import the built-in modules.

Here are some examples of importing the modules. 

math

import math
# from math import factorial

# pi
print(math.pi)


# 2 x 2 x 2
print('2 x 2 x 2 =', math.pow(2, 3))


# Factorial
print('3!=',math.factorial(3))
print(math.factorial(984))


# ceil()
print(math.ceil(3.1))


# floor()
print(math.floor(3.9))


# sqrt() 
print(math.sqrt(5))

calendar

import calendar
# calendar()

cal = calendar.calendar(2019)
print(cal)
# prcal() : print calendar

calendar.prcal(2022)
# prmonth() :print month
calendar.prmonth(2022,11)

# weekday() : week information
# Mon(0),Tue(1),Wed(2),Thur(3),Fri(4),Sat(5),Sun(6)
weekday = calendar.weekday(2022,11,28)
print('weekday:', weekday)

random

import random

# random() : 0.0 ~ 1.0 random number
r1 = random.random()
print('r1=', r1)

# randint(a, b) : a ~ b random interger
r2 = random.randint(1, 10)
print('r2=', r2)

# 1 ~ 45 random number
r3 = random.randint(1, 45)
print('r3=', r3)

# choice() : choose randomly in the list
list = ['red','orange','yellow','green','blue','navy','purple']
r4 = random.choice(list)
print('r4=', r4)

Lottery program Example 

import random

lot = []                           # list

# lot.append(random.randint(1,45))
# lot.append(random.randint(1,45))
# print(lot)

while True:
    r = random.randint(1,45)     
    if r not in lot:              
        lot.append(r)
        if len(lot) == 6:         
            break               

print(sorted(lot))

time

time() function returns the number of seconds passed since the epoch. For the Unix system, January 1, 1970, 00:00:00 at UTC is epoch (the point where time begins).

import time

print(time.time())

#localtime()
print(time.localtime(time.time()))

print(time.asctime(time.localtime(time.time())))

print(time.ctime())

print(time.strftime('%x', time.localtime(time.time())))
print(time.strftime('%c', time.localtime(time.time())))
print(time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(time.time())))

#sleep()
for i in range(10):         
    print(i)
    time.sleep(2)

web browser

import webbrowser

webbrowser.open('http://www.google.com')

webbrowser.open('http://www.naver.com')

webbrowser.open_new('member.html')

custom module Example 1) 

mypi = 3.14

def area(r):
    return mypi * r * r

Importing mymath (custom module)

import mymath

print(mymath.mypi)          # 3.14

print(mymath.area(5))       # 78.5

custom module Example 2) 

def plus(a,b):
    return a+b

def minus(a,b):
    return a-b

def multiply(a,b):
    return a*b

def divide(a,b):
    return a/b

Importing calculator (custom module) 

import calculator

print(calculator.plus(10, 5))
print(calculator.minus(10, 5))
print(calculator.multiply(10, 5))
print(calculator.divide(10, 5))

When you import some parts of the module, you will only be able to use the imported functions or variables.

# from  module import variable/function
from calculator import plus     
from calculator import minus   

print(calculator.plus(10, 5))   # error
print(plus(10, 5))
print(minus(10, 5))

print(multiply(10, 5))          # error
print(divide(10, 5))            # error

To import all the variables and functions

from calculator import *

print(plus(10, 5))
print(minus(10, 5))
print(multiply(10, 5))
print(divide(10, 5))

To use alias 

This is the most used way in Python.

import calculator  as c

print(c.plus(10,5))
print(c.minus(10,5))
print(c.multiply(10,5))
print(c.divide(10,5))

You can also install external modules and import them

c:\> pip install numpy
c:\> pip install pandas
c:\> pip install tensorflow


import numpy as np
import pandas as pd
import tensorflow as tf

To see if the modules are installed, go to settings -Python Interpreter and check.

Packages in Python are directories that contain modules. It is like a folder.

To create a graph with matplotlib.

import matplotlib.pyplot as plt

plt.plot([1,2,3,4,5,6,7,8,9,8,7,6,5,4,3,2,1])
plt.ylabel('some numbers')
plt.show()