A Taste of Python (Mon Oct 14, 2024)

Type an expression and press Shift + Enter to execute the cell.

1 + 2

3

A Taste of Python

Python is a very simple language, yet very powerful.

Python is simple

print("hello, wolrd!")

hello, wolrd!

1 + 2

3

Python is dynamically typed

x = 1
y = 2
x + y

3

x = 1
print(x)

x = "hello"
print(x)

1
hello

While variables do not have types associated with them, the values do have types and Python is very strict about them.

1 + "2"

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[7], line 1
----> 1 1 + "2"

TypeError: unsupported operand type(s) for +: 'int' and 'str'

Python uses indentation

# invalid python program

x = 1
  y = 2
x + y

  Cell In[8], line 4
    y = 2
    ^
IndentationError: unexpected indent

marks = 50

if marks > 35:
    print("pass")
else:
    print("fail")

pass

Another example:

numbers = [1, 2, 3, 4]

for n in numbers:
    print(n)
print("done")

1
2
3
4
done

Python is Expressive

Sum of square of all even numbers below one million.

sum([n*n for n in range(1000000) if n%2 == 0])

166666166667000000

!head /usr/share/dict/words

A
AA
AAA
AA's
AB
ABC
ABC's
ABCs
ABM
ABM's

!wc -l /usr/share/dict/words

104334 /usr/share/dict/words

Can you find the largest word in the dictionary?

max([3, 4, 5, 8, 2])

8

max(["one", "two", "three", "four", "five"])

'two'

max(["one", "two", "three", "four", "five"], key=len)

'three'

max(open("/usr/share/dict/words"), key=len)

"electroencephalograph's\n"

How to find the top 5 words?

sorted(open("/usr/share/dict/words"), key=len)[-5:]

['counterrevolutionaries\n',
 "counterrevolutionary's\n",
 "electroencephalogram's\n",
 'electroencephalographs\n',
 "electroencephalograph's\n"]

Python is Productive

This requires a library called requests. You can install it by running:

!python -m pip install requests

Requirement already satisfied: requests in /home/anand/.rye/py/cpython@3.12.3/lib/python3.12/site-packages (2.32.3)
Requirement already satisfied: charset-normalizer<4,>=2 in /home/anand/.rye/py/cpython@3.12.3/lib/python3.12/site-packages (from requests) (3.3.2)
Requirement already satisfied: idna<4,>=2.5 in /home/anand/.rye/py/cpython@3.12.3/lib/python3.12/site-packages (from requests) (3.7)
Requirement already satisfied: urllib3<3,>=1.21.1 in /home/anand/.rye/py/cpython@3.12.3/lib/python3.12/site-packages (from requests) (2.2.2)
Requirement already satisfied: certifi>=2017.4.17 in /home/anand/.rye/py/cpython@3.12.3/lib/python3.12/site-packages (from requests) (2024.7.4)

import requests

url = "https://api.github.com/search/repositories"
params = {
    "q": "ISI Bangalore"
}
data = requests.get(url, params=params).json()

data.keys()

dict_keys(['total_count', 'incomplete_results', 'items'])

data['total_count']

4

data['items'][0]

{'id': 832589430,
 'node_id': 'R_kgDOMaBOdg',
 'name': 'isi-fcp',
 'full_name': 'anandology/isi-fcp',
 'private': False,
 'owner': {'login': 'anandology',
  'id': 7569,
  'node_id': 'MDQ6VXNlcjc1Njk=',
  'avatar_url': 'https://avatars.githubusercontent.com/u/7569?v=4',
  'gravatar_id': '',
  'url': 'https://api.github.com/users/anandology',
  'html_url': 'https://github.com/anandology',
  'followers_url': 'https://api.github.com/users/anandology/followers',
  'following_url': 'https://api.github.com/users/anandology/following{/other_user}',
  'gists_url': 'https://api.github.com/users/anandology/gists{/gist_id}',
  'starred_url': 'https://api.github.com/users/anandology/starred{/owner}{/repo}',
  'subscriptions_url': 'https://api.github.com/users/anandology/subscriptions',
  'organizations_url': 'https://api.github.com/users/anandology/orgs',
  'repos_url': 'https://api.github.com/users/anandology/repos',
  'events_url': 'https://api.github.com/users/anandology/events{/privacy}',
  'received_events_url': 'https://api.github.com/users/anandology/received_events',
  'type': 'User',
  'site_admin': False},
 'html_url': 'https://github.com/anandology/isi-fcp',
 'description': 'Course respository for the Fundamentals of Computing and Programming at ISI Bangalore',
 'fork': False,
 'url': 'https://api.github.com/repos/anandology/isi-fcp',
 'forks_url': 'https://api.github.com/repos/anandology/isi-fcp/forks',
 'keys_url': 'https://api.github.com/repos/anandology/isi-fcp/keys{/key_id}',
 'collaborators_url': 'https://api.github.com/repos/anandology/isi-fcp/collaborators{/collaborator}',
 'teams_url': 'https://api.github.com/repos/anandology/isi-fcp/teams',
 'hooks_url': 'https://api.github.com/repos/anandology/isi-fcp/hooks',
 'issue_events_url': 'https://api.github.com/repos/anandology/isi-fcp/issues/events{/number}',
 'events_url': 'https://api.github.com/repos/anandology/isi-fcp/events',
 'assignees_url': 'https://api.github.com/repos/anandology/isi-fcp/assignees{/user}',
 'branches_url': 'https://api.github.com/repos/anandology/isi-fcp/branches{/branch}',
 'tags_url': 'https://api.github.com/repos/anandology/isi-fcp/tags',
 'blobs_url': 'https://api.github.com/repos/anandology/isi-fcp/git/blobs{/sha}',
 'git_tags_url': 'https://api.github.com/repos/anandology/isi-fcp/git/tags{/sha}',
 'git_refs_url': 'https://api.github.com/repos/anandology/isi-fcp/git/refs{/sha}',
 'trees_url': 'https://api.github.com/repos/anandology/isi-fcp/git/trees{/sha}',
 'statuses_url': 'https://api.github.com/repos/anandology/isi-fcp/statuses/{sha}',
 'languages_url': 'https://api.github.com/repos/anandology/isi-fcp/languages',
 'stargazers_url': 'https://api.github.com/repos/anandology/isi-fcp/stargazers',
 'contributors_url': 'https://api.github.com/repos/anandology/isi-fcp/contributors',
 'subscribers_url': 'https://api.github.com/repos/anandology/isi-fcp/subscribers',
 'subscription_url': 'https://api.github.com/repos/anandology/isi-fcp/subscription',
 'commits_url': 'https://api.github.com/repos/anandology/isi-fcp/commits{/sha}',
 'git_commits_url': 'https://api.github.com/repos/anandology/isi-fcp/git/commits{/sha}',
 'comments_url': 'https://api.github.com/repos/anandology/isi-fcp/comments{/number}',
 'issue_comment_url': 'https://api.github.com/repos/anandology/isi-fcp/issues/comments{/number}',
 'contents_url': 'https://api.github.com/repos/anandology/isi-fcp/contents/{+path}',
 'compare_url': 'https://api.github.com/repos/anandology/isi-fcp/compare/{base}...{head}',
 'merges_url': 'https://api.github.com/repos/anandology/isi-fcp/merges',
 'archive_url': 'https://api.github.com/repos/anandology/isi-fcp/{archive_format}{/ref}',
 'downloads_url': 'https://api.github.com/repos/anandology/isi-fcp/downloads',
 'issues_url': 'https://api.github.com/repos/anandology/isi-fcp/issues{/number}',
 'pulls_url': 'https://api.github.com/repos/anandology/isi-fcp/pulls{/number}',
 'milestones_url': 'https://api.github.com/repos/anandology/isi-fcp/milestones{/number}',
 'notifications_url': 'https://api.github.com/repos/anandology/isi-fcp/notifications{?since,all,participating}',
 'labels_url': 'https://api.github.com/repos/anandology/isi-fcp/labels{/name}',
 'releases_url': 'https://api.github.com/repos/anandology/isi-fcp/releases{/id}',
 'deployments_url': 'https://api.github.com/repos/anandology/isi-fcp/deployments',
 'created_at': '2024-07-23T10:25:25Z',
 'updated_at': '2024-10-13T18:59:50Z',
 'pushed_at': '2024-10-13T19:00:21Z',
 'git_url': 'git://github.com/anandology/isi-fcp.git',
 'ssh_url': 'git@github.com:anandology/isi-fcp.git',
 'clone_url': 'https://github.com/anandology/isi-fcp.git',
 'svn_url': 'https://github.com/anandology/isi-fcp',
 'homepage': 'https://anandology.github.io/isi-fcp/',
 'size': 2867,
 'stargazers_count': 6,
 'watchers_count': 6,
 'language': 'C',
 'has_issues': True,
 'has_projects': True,
 'has_downloads': True,
 'has_wiki': True,
 'has_pages': True,
 'has_discussions': True,
 'forks_count': 0,
 'mirror_url': None,
 'archived': False,
 'disabled': False,
 'open_issues_count': 0,
 'license': None,
 'allow_forking': True,
 'is_template': False,
 'web_commit_signoff_required': False,
 'topics': [],
 'visibility': 'public',
 'forks': 0,
 'open_issues': 0,
 'watchers': 6,
 'default_branch': 'main',
 'score': 1.0}

data['items'][0]['full_name']

'anandology/isi-fcp'

for repo in data['items']:
    print(repo['full_name'])

anandology/isi-fcp
isibangculturalcommittee/isibangculturalcommittee.github.io
MathClubISIB/mathclubisib.github.io
sudiptarakshit/ML-Modules-ISI

Let’s put all of this together.

import requests

url = "https://api.github.com/search/repositories"
params = {
    "q": "hyperbolic geometry language:python"
}
data = requests.get(url, params=params).json()

for repo in data['items']:
    print(repo['full_name'])

cduck/hyperbolic
evfro/HyperbolicRecommenders
Eloind/Hyperbolic-Geometry
yankai-chen/LKGR
tjweisman/geometry_tools
Labardini/Hyperbolic-GeometPy
mountain/hyperbolic-wythoff
ya-wei-eileen-lin/HyperbolicDiffusionDistance
nunukim/explore_hyperbolic_geometry
nbubis/Poincare
trevorBajkowski/hyperbolicPoincareDiskGeometry
TinfoilHat0/Hyperbolic-Generator
hdbray/hyperbolic_geometry
calwoo/hyperbolic
JWKennington/pyperbolic
stla/PyMobiusHyperbolic
MonkeyUnderMountain/PopularizeGeometry
asahidari/gyrovector_hyperbolic_b3d
DRWardrope/TFGeoTests
drewitz/VIPer
zbovaird/UHG-Library
LuckyGirl-XU/STGN
Rajwrita/Poincare-Embeddings
AnoushkaVyas/HyperCode
BStandage/CuttingSequence
mountain/sunspot

url = "https://api.frankfurter.app/latest"
params = {"base": "USD", "symbols": "INR"}

requests.get(url, params=params).json()

{'amount': 1.0, 'base': 'USD', 'date': '2024-10-11', 'rates': {'INR': 84.07}}

data = requests.get(url, params=params).json()
data['rates']['INR']

84.07

Rose Curves

https://en.wikipedia.org/wiki/Rose_(mathematics)

A rose is the set of points in polar coordinates specified by the polar equation

\(r=a\cos(k\theta )\)

or in Cartesian coordinates using the parametric equations

\[ \displaystyle {\begin{aligned}x&=r\cos(\theta )=a\cos(k\theta )\cos(\theta )\\y&=r\sin(\theta )=a\cos(k\theta )\sin(\theta )\end{aligned}} \]

We need numpy and matplotlib. You can install them by running:

!python -m pip install numpy matplotlib

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(-10, 10)

x

array([-10,  -9,  -8,  -7,  -6,  -5,  -4,  -3,  -2,  -1,   0,   1,   2,
         3,   4,   5,   6,   7,   8,   9])

y = x*x

y

array([100,  81,  64,  49,  36,  25,  16,   9,   4,   1,   0,   1,   4,
         9,  16,  25,  36,  49,  64,  81])

plt.plot(x, y)
plt.grid()

Ploting a circle

angles = np.linspace(0, 2*np.pi, 100)

np.linspace(1, 10, 5)

array([ 1.  ,  3.25,  5.5 ,  7.75, 10.  ])

r = 1

theta = np.linspace(0, 2*np.pi, 100)
x = r * np.cos(theta)
y = r * np.sin(theta)

plt.figure(figsize=(4, 4))
plt.plot(x, y)
plt.grid()

Now let’s try rose curves.

k = 5
a = 1

theta = np.linspace(0, 2*np.pi, 1000)
r = a * np.cos(k*theta)
x = r * np.cos(theta)
y = r * np.sin(theta)

plt.figure(figsize=(4, 4))
plt.plot(x, y)
plt.grid()

Symbolic Computation

!pip install sympy

Defaulting to user installation because normal site-packages is not writeable
Requirement already satisfied: sympy in /home/anand/.local/lib/python3.10/site-packages (1.12)
Requirement already satisfied: mpmath>=0.19 in /home/anand/.local/lib/python3.10/site-packages (from sympy) (1.3.0)

from sympy import *

x, y = symbols("x y")

x

\(\displaystyle x\)

y

\(\displaystyle y\)

a = 2*x + 3* y + 2 

a

\(\displaystyle 2 x + 3 y + 2\)

diff(sin(x))

\(\displaystyle \cos{\left(x \right)}\)

a = diff(sin(x)*exp(x), x)

a

\(\displaystyle e^{x} \sin{\left(x \right)} + e^{x} \cos{\left(x \right)}\)

integrate(a, x)

\(\displaystyle e^{x} \sin{\left(x \right)}\)