Modules and Scripts

problems

• Write a function repeat which takeks function as argument and , initial value , n an integer. it repeated calling of function n times.

>>> repeat(lambda x: 2*x, 1, 5)
32

twice(twice(twice(twice(twice(1)))))

• Write a function compose which composed two functions

>>> f = lambda x:2*x
>>> g = lambda x:x*x
>>> fg = compose(f, g)
>>> fg(2) ## f(g(2))
8

def repeat(func, initial_value, n):
    r = initial_value
    for i in range(n):
        r = func(r)
        
    return r

repeat(lambda x: 1/x, 5,  25)

0.2

def repeat_list(func, initial_value, n):
    r = initial_value
    results = []
    for i in range(n):
        r = func(r)
        results.append(r)
    return results

repeat_list(lambda x:x+1/x, 10, 50)

[10.1,
 10.199009900990099,
 10.297058634122804,
 10.394173745877744,
 10.490381489220171,
 10.585706907178288,
 10.680173909596604,
 10.773805343734718,
 10.866623059304596,
 10.958647968473018,
 11.04990010129788,
 11.140398657016274,
 11.230162051557832,
 11.319207961617632,
 11.407553365588555,
 11.495214581622534,
 11.58220730306322,
 11.66854663146874,
 11.754247107422026,
 11.839322739307336,
 11.923787030214783,
 12.0076530031197,
 12.090933224470216,
 12.173639826304404,
 12.255784527007577,
 12.337378650810614,
 12.418433146121439,
 12.498958602773941,
 12.578965268271503,
 12.65846306309588,
 12.737461595146376,
 12.815970173368983,
 12.893997820630362,
 12.971553285887229,
 13.048645055697708,
 13.125281365117694,
 13.201470208021865,
 13.277219346886138,
 13.352536322065472,
 13.427428460598543,
 13.501902884568434,
 13.575966519046425,
 13.649626099644024,
 13.72288817969661,
 13.795759137100427,
 13.868245180823148,
 13.940352357106907,
 14.012086555381327,
 14.083453513903,
 14.154458825136699]

compose  = lambda f,g: lambda x:f(g(x)) 

f = compose(lambda x:2*x, lambda x:x*x)

f(2)

8

def compose(f, g):
    def composed(x):
        return f(g(x))
    
    return composed

Modules and Scripts

#if else, while, for --> these are not functions or variables can not be passed as function parameters

def add(x, y):
    return x+y

lambda x,y: x+y

<function __main__.<lambda>(x, y)>

import math

math.sin(3.14)

0.0015926529164868282

math.log(1)

0.0

math.pi

3.141592653589793

import os

os.getcwd() # get current working directory!

'/home/vikrant/trainings/2021/pccoe-python-ml'

os.listdir() # this returns contents if current working dorectory

['index.html',
 'Lecture6-Comprehensions-1.ipynb',
 'presenty5.txt',
 'Lecture10-Modules-and-Scripts.html',
 'sample.html',
 'presenty3.txt',
 'Welcome.html',
 'Lecture9-Functions2.ipynb',
 'Lecture10-Modules-and-Scripts.ipynb',
 'push',
 'Lecture4-Working_With_Data.html',
 'presenty8.txt',
 'joy.py',
 'presenty6.txt',
 'Lecture2-Quick_Tour.ipynb',
 'Lecture7-Recap.html',
 'sample.ipynb',
 '#presenty4.txt#',
 '__pycache__',
 'Untitled.html',
 'Lecture4-Working_With_Data.ipynb',
 'Lecture5-Comprehensions.html',
 'Modules-and-Scripts.html',
 'Lecture1-Fundamental_ideas_of_programming.ipynb.ipynb',
 'index.ipynb',
 'Lecture8-Functions.ipynb',
 'Lecture7-Recap.ipynb',
 'presenty5.txt~',
 'Lecture9-Functions2.html',
 'Lecture6-Comprehensions-1.html',
 'test.html',
 'Lecture5-Comprehensions.ipynb',
 'Lecture6-Recap.html',
 'Lecture3-Quick_Tour.ipynb',
 'Lecture1-Fundamental_ideas_of_programming.ipynb.html',
 '#google.txt#',
 'Lecture8-Functions.html',
 'Makefile',
 'Lecture2-Quick_Tour.html',
 '.ipynb_checkpoints',
 'presenty9.txt',
 'Lecture3-Quick_Tour.html',
 'presenty7.txt']

os.listdir("/etc/ssh/")

['ssh_host_ed25519_key',
 'ssh_host_rsa_key.pub',
 'ssh_host_ecdsa_key.pub',
 'ssh_config.d',
 'ssh_host_ecdsa_key',
 'sshd_config',
 'ssh_host_ed25519_key.pub',
 'ssh_host_rsa_key',
 'ssh_import_id',
 'moduli',
 'ssh_config',
 'sshd_config.d']

"\n \t"

'\n \t'

"c:\\Program Files\Python3"

'c:\\Program Files\\Python3'

r"c:\Program Files\Python3"

'c:\\Program Files\\Python3'

os.path.sep

'/'

"\\"

'\\'

current_dierctory = os.getcwd()

current_dierctory

'/home/vikrant/trainings/2021/pccoe-python-ml'

"/".join([current_dierctory, "index.html"]) # it will fail on windows

'/home/vikrant/trainings/2021/pccoe-python-ml/index.html'

os.path.sep.join([current_dierctory, "index.html"]) # platform independent code

'/home/vikrant/trainings/2021/pccoe-python-ml/index.html'

os.path.isdir("index.html") # whenever path of a file does not start with / on unix, c: on windows ..
                            #then the path is called relative path

False

os.path.isdir("ssh_config.d") # relative path which is wrong!

False

os.path.isdir("/etc/ssh/ssh_config.d") # absolute path

True

os.path.exists("ssh_config.d")

False

os.path.exists("/etc/ssh/ssh_config.d")

True

os.path.getsize("index.html") # given size of file in bytes

571989

os.path.getsize(os.getcwd())

4096

def compute_foldersize(folderpath):
    contents = os.listdir(folderpath)
    total_size = 0
    for file in contents:
        path = os.path.sep.join([folderpath, file])
        if os.path.isdir(path):
            total_size += compute_foldersize(path)
        else:
            total_size += os.path.getsize(path)
            
    return total_size/(1024*1024)

compute_foldersize(os.getcwd())

10.674447420487922

Problems

• Write a function find_ipynb to find all .ipynb files in given directory (not recursive)

  >>> find_ipynb(".")
  ['index.ipynb','Lecture1.ipynb','Lecture2.ipynb']

• Write a function find_txt_recursive to find all .txt files recursively!

  >>> find_txt_recursively("/home/training/")
  [traning/2021/pccoe/presenty1.txt, ...]

  For second problem you can write a recursive function or make use os.walk. make use of help(os.walk)

os.path.isfile("index.html")

True

Writing your own modules

Any python file (.py) in current working directory can be imported as python module. If the py file that you want to make use of is not in current working directory, then you set the folder path when the file is, as PYTHONPATH.

import mymodule

mymodule.say_hello("vikrant")

Hello Vikrant

mymodule.welcome("vikrant")

Welcome Vikrant

import mymodule1

mymodule1.data

42

Writing scripts

scripts are .py files but it has got more than just definations