Chapter 2: Functions & Modularization¶
In [1]:
numbers = [7, 11, 8, 5, 3, 12, 2, 6, 9, 10, 1, 4]
In [2]:
sum(numbers)
Out[2]:
78
In [4]:
id(sum)
Out[4]:
139940703477088
In [6]:
type(sum)
Out[6]:
builtin_function_or_method
In [10]:
callable(sum)
Out[10]:
True
In [12]:
callable(numbers)
Out[12]:
False
Constructors¶
In [13]:
int(7.0)
Out[13]:
7
In [14]:
int("7")
Out[14]:
7
In [15]:
int(7.99)
Out[15]:
7
In [16]:
round(7.99)
Out[16]:
8
In [19]:
float(7)
Out[19]:
7.0
In [20]:
str(7)
Out[20]:
'7'
In [21]:
id(int)
Out[21]:
94623097764960
In [23]:
type(int)
Out[23]:
type
In [25]:
callable(int)
Out[25]:
True
Function Definitions¶
In [27]:
def average_evens(integers):
"""Calculate the average of all even numbers in a list.
Args:
integers (list of int's): whole numbers to be averaged
Returns:
average (float)
"""
evens = [n for n in integers if n % 2 == 0]
average = sum(evens) / len(evens)
return average
In [28]:
average_evens
Out[28]:
<function __main__.average_evens(integers)>
In [29]:
id(average_evens)
Out[29]:
139940571731424
In [30]:
type(average_evens)
Out[30]:
function
In [32]:
callable(average_evens)
Out[32]:
True
Function Calls¶
In [37]:
average_evens([7, 11, 8, 5, 3, 12, 2, 6, 9, 10, 1, 4])
Out[37]:
7.0
In [38]:
average_evens(numbers)
Out[38]:
7.0
In [39]:
result = average_evens(numbers)
In [40]:
result
Out[40]:
7.0
Scoping Rules¶
Local Scope disappears¶
In [41]:
integers
--------------------------------------------------------------------------- NameError Traceback (most recent call last) Cell In[41], line 1 ----> 1 integers NameError: name 'integers' is not defined
In [42]:
evens
--------------------------------------------------------------------------- NameError Traceback (most recent call last) Cell In[42], line 1 ----> 1 evens NameError: name 'evens' is not defined
Global Scope is everywhere¶
In [44]:
def average_wrong(integers):
"""Calculate the average of all even numbers in a list.
Args:
integers (list of int's): whole numbers to be averaged
Returns:
average (float)
"""
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return average
In [45]:
numbers
Out[45]:
[7, 11, 8, 5, 3, 12, 2, 6, 9, 10, 1, 4]
In [46]:
average_wrong(numbers) # correct by accident
Out[46]:
7.0
In [47]:
average_wrong([123, 456, 789])
Out[47]:
7.0
Shadowing¶
In [48]:
def average_evens(integers):
"""Calculate the average of all even numbers in a list.
Args:
integers (list of int's/float's): numbers to be averaged;
if non-whole numbers are provided, they are rounded
Returns:
average (float)
"""
numbers = [round(n) for n in integers]
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return average
In [49]:
average_evens([40.0, 41.1, 42.2, 43.3, 44.4])
Out[49]:
42.0
In [52]:
numbers
Out[52]:
[7, 11, 8, 5, 3, 12, 2, 6, 9, 10, 1, 4]
In [55]:
def average_evens(numbers):
"""Calculate the average of all even numbers in a list.
Args:
numbers (list of int's): whole numbers to be averaged
Returns:
average (float)
"""
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return average
In [56]:
average_evens(numbers)
Out[56]:
7.0
In [57]:
numbers
Out[57]:
[7, 11, 8, 5, 3, 12, 2, 6, 9, 10, 1, 4]
Positional vs. Keyword Arguments¶
In [58]:
divmod(42, 10)
Out[58]:
(4, 2)
In [59]:
divmod(10, 42)
Out[59]:
(0, 10)
In [60]:
def scaled_average_evens(numbers, scalar):
"""Calculate the scaled average of all even numbers in a list.
Args:
numbers (list of int's/float's): numbers to be averaged;
if non-whole numbers are provided, they are rounded
scalar (float): multiplies the average
Returns:
scaled_average (float)
"""
numbers = [round(n) for n in numbers]
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return scalar * average
In [61]:
scaled_average_evens(numbers, 2)
Out[61]:
14.0
In [62]:
scaled_average_evens(numbers=numbers, scalar=2)
Out[62]:
14.0
In [63]:
scaled_average_evens(scalar=2, numbers=numbers)
Out[63]:
14.0
In [64]:
scaled_average_evens(numbers, scalar=2)
Out[64]:
14.0
Modularization¶
In [68]:
def average_evens(numbers):
""" ... ... ... """
numbers = [round(n) for n in numbers]
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return average
In [69]:
def scaled_average_evens(numbers, scalar):
""" ... ... ... """
numbers = [round(n) for n in numbers]
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return scalar * average
In [70]:
def average_evens(numbers):
""" ... ... ... """
return scaled_average_evens(numbers, scalar=1)
In [71]:
def scaled_average_evens(numbers, scalar):
""" ... ... ... """
numbers = [round(n) for n in numbers]
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return scalar * average
Default Arguments¶
In [74]:
def average_evens(numbers, scalar=1):
"""Calculate the average of all even numbers in a list.
Args:
numbers (list of int's/float's): numbers to be averaged;
if non-whole numbers are provided, they are rounded
scalar (float, optional): multiplies the average; defaults to 1
Returns:
scaled_average (float)
"""
numbers = [round(n) for n in numbers]
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return scalar * average
In [75]:
average_evens(numbers)
Out[75]:
7.0
In [76]:
average_evens(numbers, 2)
Out[76]:
14.0
In [77]:
average_evens(numbers, scalar=2)
Out[77]:
14.0
Keyword-only Arguments¶
In [78]:
def average_evens(numbers, *, scalar=1):
"""Calculate the average of all even numbers in a list.
Args:
numbers (list of int's/float's): numbers to be averaged;
if non-whole numbers are provided, they are rounded
scalar (float, optional): multiplies the average; defaults to 1
Returns:
scaled_average (float)
"""
numbers = [round(n) for n in numbers]
evens = [n for n in numbers if n % 2 == 0]
average = sum(evens) / len(evens)
return scalar * average
In [79]:
average_evens(numbers)
Out[79]:
7.0
In [80]:
average_evens(numbers, scalar=2)
Out[80]:
14.0
In [81]:
average_evens(numbers, 2)
--------------------------------------------------------------------------- TypeError Traceback (most recent call last) Cell In[81], line 1 ----> 1 average_evens(numbers, 2) TypeError: average_evens() takes 1 positional argument but 2 were given