The Basics

The Basics#

Definition

Python - is an interpreted, object-oriented, high-level programming language with dynamic semantics. Its high-level builtin data structures, combined with dynamic typing and dynamic binding, make it very attractive for Rapid Application Development, as well as for use as a scripting or glue language to connect existing components together. Python.org

Editors#

​ Run in interactive mode

# first program
print ("hello world")

Coding Concepts#

  • Case sensitive

  • Space-based - tabbing has meaning

    • List appropriate use of white space and tabbing

  • Do not go more than 80 characters

  • Escape characters \n (new line) and \t (tab)

  • Each line is its own command statement

  • Two or more physical lines may be joined into logical lines using backslash characters (\)

Variables#

The purpose of a variable is to store one value. This could be a string, integer, float, Boolean, char, or object.

Variable names

  • must start with a letter

  • may contain the underscore

  • may contain numbers

  • case sensitive

The equal sign is used to assign a value to the variable

dogname = "spot"
salary = 100000.00
age = 4

Order of Operations#

  • () parenthesis

  • ** power

  • + - add subtract

  • * \ multiple divide

  • // integer division

Comments#

Note

Comments allow the programmer to document their code. It is very import to document your code. Comments can be single lined, which is desginated by using a # followed by a space. Or they can be multiple lined in which they are enclosed by three double quotes “”” .

Datatypes#

"""
data types
storing variables
    variable names should be descriptive
"""

#integers
a = 42
print(a)
print(type(a))

# = floats
b = 42.0
print(b)
print(type(b))

# = strings
c = "forty two"
print(c)
print(type(c))

# = booleans  True / False
d = True
print(d)
print(type(d))

# = null
e = None
print(e)
print(type(e))

# ---------------------------------------
#   containers - discuss more in future - just show
# ---------------------------------------

print("\n*** Lists ***\n")      # Explain \n and \t

### LISTS ###
## properties: ordered, iterable, mutable, can contain multiple data types
mylista = [1,2,3,4]
print(mylista)

mylistb = ["larry", "curly", "moe"]
print(mylistb)

mylistc = [42, 42.0, "forty two", True, ['Tom', 'Dick', 'Harry']]
print(mylistc)

### TUPLES ###
## properties: ordered, iterable, immutable, can contain multiple data types
## like lists, but they don't change size
mytuplea = (1,2,3)
print(mytuplea)

mytupleb = ("Ducks", "Goats", "Cows")
print(mytupleb)

mytuplec = (1, 1.1, "one", False, [42, 43, 44, 45])
print(mytuplec)
print(type(mytuplec))


### DICTIONARIES ###
## properties: unordered, iterable, mutable, can contain multiple data types
## made of key-value pairs
## keys must be unique, and can be strings, numbers, or tuples
## values can be any type

# ---------------------------------------

print("\n*** Dictionaries ***\n")

### DICTIONARIES ###
## properties: unordered, iterable, mutable, can contain multiple data types
## made of key-value pairs
## keys must be unique, and can be strings, numbers, or tuples
## values can be any type

mydict = {"key1": "value1", "key2": "value2", "key3": "value3" }
print(mydict)

# student number, last name
mydict1 = {111 : "Smith", 222 : "Doe", 333 : "Baker"}
print(mydict1)
print(type(mydict1))

#show error
mydict1 = {111 : "Smith", 222 : "Doe", 333 : "Baker", 111 : "Adam"}

# ---------------------------------------

print("\n*** Sets ***\n")

### SETS ###
## properties: unordered, iterable, mutable, can contain multiple data types
## made of unique elements (strings, numbers, or tuples)
## like dictionaries, but with keys only (no values)

#like dictionaries, but leave out the values
myset1 = {'python', 'r', 'java', 'c#'} 
print(myset1)

myset2 = {1, 2, 3, 4, 5, 6}
print(myset2)
print(type(myset2))

#show error
myset3 = {11,22,33,33, 44,55}
print(myset3)

# -------------------------------------

Example Showing Mathematical Operations

print("Get and display input " )
dogname = input("Enter a dog name ")
dogage = float(input("Enter the dog age in years  "))

# numbers must be in a str() function
print("Dog name = " +  dogname + "  age = " + str(dogage))
print("\n\n")



print("-- operations review --")
print("Parenthesis 2 + 5 * 7 vs (2 + 5) * 7")
x = 2 + 5 * 7
print(x)
x = (2 + 5) * 7
print(x)

print("3 to the power of 3 3**3")
x = 3**3
print(x)

a = 10.5
b = 2.5


print("Add and subtract 10.5 2.5")
x = a + b
print(x)

x = a - b
print(x)

print("Multiple and divide 10.5 2.5")

x = a * b
print(x)

End Of Topic

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