3.1.2_useful_python.md

DU Class Notes Table of Contents

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• Course Overview
• Tool Setup
  • Tool Setup - Mac
  • Tool Setup - Windows
    • Windows - alternate setup using wsl
    • Tool Setup - Windows WSL
    • Window - alternative setup using docker
• Online Research Tips
• Further Reading and Helpful Links
  • See the great work by Matt Watkins collecting examples. Sorry example links only accessible to students of the DU AI Courses.
  • Resources
  • Cheatsheets & Tips
    • Scientific python cheatsheet by IPGD
    • Useful Python tips
  • Books
  • Articles
  • Subscriptions
• Career Engagement
• Data Sources

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Useful Python Stuff

Clearing the screen

import os
 
# Clearing the Screen
os.system('cls')

Check value type

if type(mydict) is dict:
if type(mylist) is list:
if type(myint) is int:
if type(myfloat) is float:
if type(mystring) is string:

check if main program

Add this for code your intend to run directly from the command line.

if __name__ == "__main__"

See more here: What Does if name == "main" Do in Python?

Special Functions

map

The map() function executes a specified function for each item in an iterable. The item is sent to the function as a parameter.

Syntax

map(function, iterables)

Example

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

x = map(myfunc, ('apple', 'banana', 'cherry'), ('orange', 'lemon', 'pineapple'))

print(x)

#convert the map into a list, for readability:
print(list(x))

returns:

<map object at 0x034244F0>
['appleorange', 'bananalemon', 'cherrypineapple']

Parameter	Description
function	Required. The function to execute for each item
iterable	Required. A sequence, collection or an iterator object. You can send as many iterables as you like, just make sure the function has one parameter for each iterable.

lambda

A lambda function is a small anonymous function.

A lambda function can take any number of arguments, but can only have one expression.

Syntax

lambda arguments : expression

Example 1

x = lambda a, b : a * b
print(x(5, 6))

Example 2

x = lambda a, b : a * b
print(x(5, 6))

Example 3

x = lambda a, b, c : a + b + c
print(x(5, 6, 2))

filter

The filter() function returns an iterator where the items are filtered through a function to test if the item is accepted or not.

Syntax

filter(function, iterable)

Parameter Values

Parameter	Description
function	A Function to be run for each item in the iterable
iterable	The iterable to be filtered

Example

ages = [5, 12, 17, 18, 24, 32]

def myFunc(x):
  if x < 18:
    return False
  else:
    return True

adults = filter(myFunc, ages)

for x in adults:
  print(x)

returns:

18
24
32

Docstring

See the Docstring tutorial