Python functions

def add_numbers(x,y,z=None):
    if (z==None):
        return x+y
    else:
        return x+y+z
 
print(add_numbers(1, 2))
print(add_numbers(1, 2, 3))

def add_numbers(x, y, z=None, flag=False):
    if (flag):
        print('Flag is true!')
    if (z==None):
        return x + y
    else:
        return x + y + z
 
print(add_numbers(1, 2, flag=True))

def add_numbers(x,y):
    return x+y
 
a = add_numbers
a(1,2)

Types and sequences

type('This is a string')
type(None)
type(1)
type(1.0)
type(add_numbers)
 
x = (1, 'a', 2, 'b')
type x     tuples are immutable wheras lists are mutable
x = [1, 'a', 2, 'b']   list
x.append(3.3)
 
for item in x:
   print(item)
OR
i=0
while( i != len(x) ):
    print(x[i])
    i = i + 1
 
[1,2] + [3,4]
 
[1]*3
 
1 in [1, 2, 3]
 
x[-4:-2]
 
firstname = 'Christopher'
lastname = 'Brooks'
 
print(firstname + ' ' + lastname)
print(firstname*3)
print('Chris' in firstname)
 
firstname = 'Christopher Arthur Hansen Brooks'.split(' ')[0] # [0] selects the first element of the list
lastname = 'Christopher Arthur Hansen Brooks'.split(' ')[-1] # [-1] selects the last element of the list
print(firstname)
print(lastname)
 
'Chris' + 2
'Chris' + str(2)
 
x = {'Christopher Brooks': 'brooksch@umich.edu', 'Bill Gates': 'billg@microsoft.com'}
x['Christopher Brooks'] # Retrieve a value by using the indexing operator
 
x['Kevyn Collins-Thompson'] = None
x['Kevyn Collins-Thompson']
 
for name in x:
    print(x[name])
 
for email in x.values():
    print(email)
 
for name, email in x.items():
    print(name)
    print(email)
 
x = ('Christopher', 'Brooks', 'brooksch@umich.edu')
fname, lname, email = x
 
x = ('Christopher', 'Brooks', 'brooksch@umich.edu', 'Ann Arbor')
fname, lname, email = x
 
more on strings
 
sales_record = {
'price': 3.24,
'num_items': 4,
'person': 'Chris'}
 
sales_statement = '{} bought {} item(s) at a price of {} each for a total of {}'
 
print(sales_statement.format(sales_record['person'],
                             sales_record['num_items'],
                             sales_record['price'],
                             sales_r