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HelloWorld_Types.py

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# A first Python script

import sys

import os

import math

import random

import re

# Main built-in functions

# Print out description about passed object

help(list)

help(list.append)

A = []

help(A)

# Returns the attributes of the passed object

dir(list)

dir(A)

# Returns the type of the object (where the name references)

type(A)

# The Zen of Python, by Tim Peters

import this

# Print OS name

print(sys.platform)

print(os.getcwd())

# Print 2^32

print('2^32: ' + str(2 ** 32) + ' bytes')

# String repetition

x = 'Spam! '

print(x * 8)

# Math example

print(math.pi)

print(random.randint(10, 20))

# String examples>>> line = 'aaa,bbb,ccccc,dd'

myString = 'Spam'

print(myString.find('pa'))

print(myString)

print(myString.replace('pa', 'XYZ'))

print(myString)

# Find the offset of a substring in myString

line = 'aaa,bbb,ccccc,dd'

print(line.split(','))

print(myString.upper())

print(myString.isalpha())

print(myString.isdecimal())

# Split on a delimiter into a list of substrings

line = 'aaa,bbb,ccccc,dd\n'

#print line with additional NewLine in the text (from the right side)

print(line)

# print line without whitespace characters

print(line.rstrip())

# Remove whitespace characters and

print(line.rstrip().split(','))

# Regular Expressions

match = re.match('Hello[ \t]*(.*)world', 'Hello world')

match.group(1)

# List examples

myList = [1, "Test", [2, 4, 5]]

print(myList)

myList.pop(2)

print(myList)

myList.reverse()

print(myList)

myList.append("END")

print(myList)

# Matrix

matrix = [[1,2,3],[4,5,6],[7,8,9]]

print(matrix)

print(list(range(4)))

# −6 to +6 by 2 (need list() in 3.X)

print(list(range(-6, 7, 2)))

print([[str(x), x ** 3] for x in range(4)])

# Multiple values, "if" filters

print([[x, x / 2, x * 2] for x in range(-6, 7, 2) if x > 0])

# List, Set, Map based on the range

print(set(range(-5, 10, 3)))

print(list(range(-5, 10, 3)))

myMap = {str(x): x ** 3 for x in range(-5, 10, 3)}

print(myMap)

# Generator example: sum of rows

G = (sum(row) for row in matrix)

print(next(G))

print(next(G))

print(next(G))

# Set and Map with function

setSum = {sum(row) for row in matrix}

print(setSum)

# Check existence in 6

if 6 in setSum:

print(str(6) + " is found")

mapSum = {str(i) : sum(matrix[i]) for i in range(3)}

print(mapSum)

# Nested dictionaries

person = {'name': {'first': 'Bob', 'last': 'Smith'},

'jobs': ['Developer', 'Cooker'],

'age' : 36}

print(person)

person['jobs'].append('Sailor')

print(person)

# Check existence in dictionary/map

if 'name' in person:

print(person['name'])

# Print sorted keys and related values

for key in sorted(person):

print(key, '=>', person[key])

# Clear memory

person.clear()

print(person)

# Tuples - distincts in that they are immutable collections

T = (1, 2, 25, 4, 5)

print(T)

# T[2] = 5 isn't allowed

print(T.index(25))

# Files

dataFile = open('data.txt', 'w')

dataFile.write('Hello\n')

dataFile.write('world\n')

dataFile.close()

dataFile = open('data.txt', 'r')

# Print all the file as a line

print(dataFile.read())

dataFile.close()

for curLine in open('data.txt'):

print(curLine)

# Type checking - not "Pythonic"

print(type(matrix),

type(matrix[0]),

type(matrix[0][1]) == int,

isinstance(matrix, list))

list1 = [1, 2, 3]

print(list1[2])

### Sets ###

# Create using set() constructor passing iterable object

mySet = set('Test')

mySet2 = set('Boot')

# Creates set of 1 item of the string 'Set3'

mySet3 = {'Set3'}

print(mySet.intersection(mySet2))

print(mySet2)

# Can't add List, Add, Dict, because set containts immutable objects, that is hashable

# mySet2.add(['G', 'L'])

# mySet2.add({'GOAL'})

# {1, 2, 3, 4} - {1, 2}

# {1, 2, 3, 4} & {1, 2}

# {1, 2, 3, 4} ^ {1, 2}

# {1, 2, 3, 4} > {1, 2}

# {1, 2, 3, 4} < {1, 2}

# {1, 2} < {1, 2, 3, 4}

# {1, 2} < {1, 2, 3, 4}

# {1, 2, 5} < {1, 2, 3, 4}

L1 = [1, 3, 5]

L2 = L1 # => L2 refers to the same object (only for mutable objects)

L1[0] = 200 # Changes both L2 and L1 (sure)

# Print ID of the objects => equal

print(id(L1), id(L2))

# Make copy

import copy

L2 = copy.copy(L1) # "shallow" copy

L2 = copy.deepcopy(L1) # Deep copy with nested structions

# Print ID of the objects => different, anothe object was created

print(id(L1), id(L2))

# or

L2 = list(L1) # Generage another object using list Constructor

# Comparisons

L1 == L2 # Compare values

L1 is L2 # Compare identity (the same object or not)

import sys # Get reference counter for an object

sys.getrefcount(L1)

# Print out list of arguments: sys.argv[0] is the name of the file, as in C

print([x for x in sys.argv])

# Or just

print(sys.argv)

# Comparisons

L1 = [1, 2, 3]

L2 = [1, 2, 3]

# Equal but not the same objects

print(L1 == L2, L1 is L2)

# Equal and the same objects - short strings

S1 = "Test"

S2 = "Test"

print(S1 == S2, S1 is S2)

# Equal and not the same objects - longer strings

S1 = "Long string 444444444444444 666666666666666666666666666666666666"

S2 = "Long string 444444444444444 666666666666666666666666666666666666"

print(S1 == S2, S1 is S2)