Main

## Main.PythonBasics History

May 15, 2018, at 02:27 PM by 45.56.3.173 -
Added lines 6-9:

(:html:)
<iframe width="560" height="315" src="https://www.youtube.com/embed/BdATXeUkKnw" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>
(:htmlend:)
May 14, 2018, at 03:31 PM by 45.56.3.173 -
Added lines 100-108:

Guess a number (0-10): 5
Too high
Guess a number (0-10): 3
Too high
Guess a number (0-10): 1
Too low
Guess a number (0-10): 2
Correct!
May 14, 2018, at 03:30 PM by 45.56.3.173 -
Changed lines 136-141 from:
Python has addition (+), subtraction (-), multiplication (*), division (/), and power (**) as standard mathematical operators. The [[https://docs.python.org/3/library/math.html|Math module]] is available with:

import
math

These provide a number of other mathematical operators such as shown in the example
below:
to:
Python has addition (+), subtraction (-), multiplication (*), division (/), and power (**) as standard mathematical operators. The [[https://docs.python.org/3/library/math.html|Math module]] is available by importing the math package. The math module provides a number of common mathematical operators such as shown in the example below.
Changed line 144 from:
The [[https://docs.scipy.org/doc/numpy-1.13.0/reference/routines.math.html|Numpy module]] also has many of the mathematical operators. This course uses many NumPy and SciPy built-in values and functions for scientific computing. Below is an example of using a built-in value and a trigonometric function (sine).
to:
The [[https://docs.scipy.org/doc/numpy-1.13.0/reference/routines.math.html|Numpy module]] also has many of the mathematical operators. This course uses many NumPy and SciPy built-in values and functions for scientific computing. Below is an example of using a built-in value and a trigonometric function (sine). In this case, the NumPy package is renamed as ''np'' to shorten the future references (numpy.pi => np.pi).
May 14, 2018, at 03:26 PM by 45.56.3.173 -
Changed lines 11-18 from:
myVar
myVariable
my4Variable
myVariable4
_myVariable
__myVariable
MYVARIABLE
myvariable
to:
myVar
myVariable
my4Variable
myVariable4
_myVariable
__myVariable
MYVARIABLE
myvariable
Changed lines 22-25 from:
my Variable
4myVariable
myVariable!
to:
my Variable
4myVariable
myVariable!
Changed lines 68-69 from:
There are also many built-in functions that should also be avoided when creating variable names such as:
to:
There are also many [[https://python-reference.readthedocs.io/en/latest/docs/functions/|built-in functions]] that should also be avoided when creating variable names. Some common functions are listed below.
Changed lines 73-74 from:
max      # return the maximum value
min
# return the minimum value
to:
len      # number of elements in a collection
max
# maximum value
min      # minimum value
pow      # power (e.g. pow(x,2) or use x**2)
Added line 78:
round    # nearest integer value
Changed lines 104-105 from:
Python is an object-oriented programming language. Each Python object has defining properties including the Identity (an identification number), Type (e.g. String, Integer, Float), and Value. Below is an example of assigning 'x' as an Integer and printing the object properties.
to:
Python is an object-oriented programming language. Each Python object has defining properties including the '''Identity''' (a memory address), '''Type''' (e.g. string, integer, floating point number), and '''Value'''. Below is an example of assigning 'x' as an Integer and printing the object properties.
Changed line 108 from:
print(x)      # print value    => 3
to:
print(x)      # print value    => 2
Changed lines 113-114 from:

to:
!!!! Python Data Types

Data can be stored a variety of formats. [[https://python-reference.readthedocs.io/en/latest/basic_data_types.html|Fundamental Data Types]] include '''Numbers''' (e.g. ''int'' and ''float''), Sequences (e.g. ''str'', ''list'', and ''tuple''), and Mappings (''dict''). Below are a few examples:

(:source lang=python:)
x=2            # integer
y=2.02          # float
z='3'          # string
print(str(x)+z) # 23
print(x+int(z)) # 5

a=[x,y,z]      # list
print(a)    # 2.02

b=(x,y)        # tuple
print(b)    # 2.02

c={'m':7,'n':8} # dictionary
print(c['m'])  # 7
(:sourceend:)

!!!! Python Math Expressions

Python has addition (+), subtraction (-), multiplication (*), division (/), and power (**) as standard mathematical operators. The [[https://docs.python.org/3/library/math.html|Math module]] is available with:

import math

These provide a number of other mathematical operators such as shown in the example below:

(:source lang=python:)
import math
x=3.1415
print(math.sin(x)) # 9.265e-05
(:sourceend:)

The [[https://docs.scipy.org/doc/numpy-1.13.0/reference/routines.math.html|Numpy module]] also has many of the mathematical operators. This course uses many NumPy and SciPy built-in values and functions for scientific computing. Below is an example of using a built-in value and a trigonometric function (sine).

(:source lang=python:)
import numpy as np
x=np.pi
print(math.sin(x))  # 1.225e-16
(:sourceend:)

The result of mathematical expressions may be slightly off the expected value such as the example above that should equal to zero for sin(pi). This is due to finite machine precision (32-bit or 64-bit) calculations that have some round-off error at the last stored digit.

!!!! Python Strings

Strings are a list of characters. Strings are combined with the addition (+) symbol and either the single or double quotes are used.

(:source lang=python:)
first = 'Tom'
last = "Smith"
name = first + ' ' + last
print(name)  # Tom Smith
(:sourceend:)

Comments can are added to Python scripts with the hash (#) symbol. When included inside a string, the comment character becomes part of the text and is no longer a comment.

(:source lang=python:)
hashtag = '#learnpython'
print(hashtag) # prints: #learnpython
(:sourceend:)

There are also special escape sequences such as newline (\n), tab indent (\t), double quote (\"), single quote (\'), and backslash (\\).

(:source lang=python:)
flight = 'Landing at\n O\'Hare International Airport'
print(flight)
# prints:
# Landing at
#  O'Hare International Airport
(:sourceend:)

To avoid using special escape sequences such as newline, a raw string identifier (r) can be used before the string definition.

(:source lang=python:)
flight = r'Landing at\n O\'Hare International Airport'
print(flight)
# prints:
# Landing at\n O\'Hare International Airport
(:sourceend:)

The easiest way to convert a number to a string is with the built-in function '''str'''. However, this method may produce a number that has too many decimal places. Numbers can be customized in floating point (f), scientific notation (e), or percentage (%) form with '''format''' such as:

(:source lang=python:)
# import the number pi
import numpy as np
x = np.pi

# format pi
print(str(x))              # 3.141592653589793
print('{:.2f}'.format(x))  # 3.14
print('{:.10f}'.format(x)) # 3.1415926536
print('{:.5e}'.format(x))  # 3.14159e+00
print('{:.3%}'.format(x))  # 314.159%
(:sourceend:)
May 14, 2018, at 01:35 PM by 45.56.3.173 -
Changed lines 5-13 from:
This tutorial is an introduction to Python basics such as how to assign a variable value or increment that value. Valid variable names are those that start with a letter (upper or lower case) or underscore. Valid variable names include:

myVariable
my4Variable
myVariable4
_myVariable
__myVariable
MYVARIABLE
myvariable
to:
This tutorial is an introduction to Python basics such as how to assign a variable value and change that value. There is also a list of reserved keywords although use of these keywords is explained later.

!!!! Python Variable Names

Valid variable names are those that start with a letter (upper or lower case) or underscore. Valid variable names include:

myVar
myVariable
my4Variable
myVariable4
_myVariable
__myVariable
MYVARIABLE

myvariable
Changed lines 20-23 from:
Invalid variable names include those that start with a number or have a space in the name such as:

my Variable
4myVariable
to:
Invalid variable names include those that start with a number, have a space in the name, or contain special characters such as:

my Variable
4myVariable
myVariable!

!!!! Python Reserved Keywords

There are reserved keywords in Python that control the flow of the program and cause unique behavior. Built-in constants include:

True    # True logical condition
False    # False logical condition
None    # Absense of a value

Note that True, False, and None are capitalized. Common reserved keywords include:

and      # logical 'and' (both conditions True)
as      # aliasing (e.g. with open(file) as f:)
assert  # internal self-check (e.g. assert x=y)
break    # break out of a loop
class    # define a new class (variables and functions)
continue # advance to next 'for' or 'while' loop
def      # define a function
del      # set a variable to 'None'
elif    # 'else if' condition of 'if' statement
else    # 'else' condition of 'if' statement
except  # catch errors
finally  # 'try' exit code
for      # 'for' loop
from    # specify package element for loading
global  # create a global variable
if      # 'if' statement
import  # load package
in      # membership operator (e.g. x in y)
is      # test for equal identification numbers
lambda  # create anonymous function
nonlocal # expand variable scope outside function
not      # logical 'not'
or      # logical 'or'
pass    # null operator when statement is required
print    # create display output line
raise    # error notification (e.g. raise Exception('Error'))
return  # return from function
try      # 'try'...'except' code structure for error catching
while    # loop until condition is not True
with    # flow control for automatic clean-up
yield    # intermediate return from function
Changed lines 68-69 from:
There are reserved keywords in Python that control the flow of the program and cause unique behavior. These reserved keywords include:
to:
There are also many built-in functions that should also be avoided when creating variable names such as:

float    # convert number to floating point type
id      # identification number
int      # convert number to integer type
max      # return the maximum value
min      # return the minimum value
range    # sequence generator
str      # convert to string type
type    # object type

These reserved keywords should be avoided when creating variable names. Most Integrated Development Environments (IDEs) for Python and text editors for Python scripts will automatically highlight the reserved keywords such as the example below where reserved keywords are highlighted in orange and green.

(
:toggle hide mycode1 button show="Show Example of Reserved Keywords":)
(:div id=mycode1:)
Changed line 85 from:
answer = randint(0,100)
to:
answer = randint(0,10)
Changed line 88 from:
guess = int(input("Guess a number: "))
to:
guess = int(input("Guess a number (0-10): "))
Added lines 97-111:
(:divend:)

!!!! Python Objects

Python is an object-oriented programming language. Each Python object has defining properties including the Identity (an identification number), Type (e.g. String, Integer, Float), and Value. Below is an example of assigning 'x' as an Integer and printing the object properties.

(:source lang=python:)
x=2            # create variable 'x'
print(x)      # print value    => 3
print(id(x))  # print id number => 1737348944
print(type(x)) # print type      => <class 'int'>
(:sourceend:)

May 14, 2018, at 12:12 PM by 45.56.3.173 -
Added lines 1-54:
(:title Python Programming Basics:)
(:keywords Python, variable naming, assignment, False, True:)
(:description Python is a versatile language but can be intimidating for first-time programmers. This tutorial is designed for beginners to get started.:)

This tutorial is an introduction to Python basics such as how to assign a variable value or increment that value. Valid variable names are those that start with a letter (upper or lower case) or underscore. Valid variable names include:

myVariable
my4Variable
myVariable4
_myVariable
__myVariable
MYVARIABLE
myvariable

Invalid variable names include those that start with a number or have a space in the name such as:

my Variable
4myVariable

There are reserved keywords in Python that control the flow of the program and cause unique behavior. These reserved keywords include:

(:source lang=python:)
from random import *
answer = randint(0,100)
correct = False
while not(correct):
guess = int(input("Guess a number: "))
if guess < answer:
print("Too low")
elif guess > answer:
print("Too high")
else:
print("Correct!")
correct = True
(:sourceend:)

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