Functions part II

def cylinder_volume(radius, height):
    return 3.14*radius**2*height

cylinder_volume(1, 2)

6.28

cylinder_volume(2, 1)# by mistake , arguments order swapped...inorrect order

12.56

cylinder_volume(radius=1, height=2)

6.28

cylinder_volume(height=2, radius=1) # order doen't matter if named parameters are given

6.28

def say_hello(name="friend"):
    print("hello", name)

say_hello("vikrant")

hello vikrant

say_hello() # is the parameter defined with default value, if not passed ..default will be taken

hello friend

import random

def jitter(data, jitter=random.random()):
    return data+jitter
    

jitter(45)

45.719416944816

for i in range(5):
    print(jitter(i))

0.7194169448159936
1.7194169448159937
2.7194169448159937
3.7194169448159937
4.719416944815993

import random

def jitter(data, jitter=None):
    if not jitter:
        jitter = random.random()
    return data+jitter
    

for i in range(5):
    print(jitter(i))

0.8775489801271318
1.5138647086694264
2.6011478633148295
3.19229987623221
4.925170727877281

def create_data(basedata=[]): #not a goot way of creating empty list in default parameters
    return [jitter(item) for item in basedata]

def appendzeros(n , basedata=[]):
    basedata.extend([0 for i in range(n)])
    return basedata

appendzeros(2, [1, 2, 3, 4])

[1, 2, 3, 4, 0, 0]

appendzeros(3, [1, 2, 3, 4])

[1, 2, 3, 4, 0, 0, 0]

appendzeros(2) # default value for basedata

[0, 0]

appendzeros(2) # this is surprise!

[0, 0, 0, 0, 0, 0]

def appendzeros(n , basedata=None):
    if basedata==None:
        basedata = []
    basedata.extend([0 for i in range(n)])
    return basedata

appendzeros(2)# basedata is now [] 

[0, 0]

appendzeros(3)# basedata is now [] 

[0, 0, 0]

variable number arguments

max(1, 2, 3, 4)

4

max(1, 2, 3)

3

def mysum(*nums):
    print(nums)

mysum(1, 2, 3)

(1, 2, 3)

mysum(1, 2)

(1, 2)

def mysum(*nums):
    s = 0 
    for i in nums:
        s += i
    return s

mysum(1, 4, 5, 6)

16

mysum(1, 1, 1, 1, 1, 1, 1, 1, 1)

9

def mysum(*nums):
    return sum(nums)

mysum(1, 2, 3, 4)

10

def foo(fixed, *args):
    print(fixed)
    print(args)

foo("hello", 2, 3, 41)

hello
(2, 3, 41)

def foo(*args, fixed): # not allowed! variable number of arguments have to come last!
    print(fixed)
    print(args)

foo(1, 2, 3, "hello")

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-45-cf5e6215f4d8> in <module>
----> 1 foo(1, 2, 3, "hello")

TypeError: foo() missing 1 required keyword-only argument: 'fixed'

values = [1, 2, 3, 4, 4]
mysum(*values) # while calling * indicates individual values from the list

14

mysum(values)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-47-504e77c64afa> in <module>
----> 1 mysum(values)

<ipython-input-40-7977d9df90be> in mysum(*nums)
      1 def mysum(*nums):
----> 2     return sum(nums)

TypeError: unsupported operand type(s) for +: 'int' and 'list'

tables = [[i*j for i in range(1, 11)] for j in range(1, 5)]

tables

[[1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
 [2, 4, 6, 8, 10, 12, 14, 16, 18, 20],
 [3, 6, 9, 12, 15, 18, 21, 24, 27, 30],
 [4, 8, 12, 16, 20, 24, 28, 32, 36, 40]]

tables[0]

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

tables[0][2]

3

tables[1][2]

6

tables[2][2]

9

tables[3][2]

12

def column(data2d, col):
    rowcount = len(data2d)
    return [data2d[r][col] for r in range(rowcount)]

column(tables, 2)

[3, 6, 9, 12]

column(tables, 3)

[4, 8, 12, 16]

def transpose(data2d):
    colcount = len(data2d[0])
    return [column(data2d, c) for c in range(colcount)]

transpose(tables)

[[1, 2, 3, 4],
 [2, 4, 6, 8],
 [3, 6, 9, 12],
 [4, 8, 12, 16],
 [5, 10, 15, 20],
 [6, 12, 18, 24],
 [7, 14, 21, 28],
 [8, 16, 24, 32],
 [9, 18, 27, 36],
 [10, 20, 30, 40]]

for item in tables:
    print(item)

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
[3, 6, 9, 12, 15, 18, 21, 24, 27, 30]
[4, 8, 12, 16, 20, 24, 28, 32, 36, 40]

for row in tables:
    print(row)

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
[3, 6, 9, 12, 15, 18, 21, 24, 27, 30]
[4, 8, 12, 16, 20, 24, 28, 32, 36, 40]

def column(data2d, col):
    return [row[col] for row in data2d]

column(tables, 2)

[3, 6, 9, 12]

first  = [1, 2, 3]
second = ("one", "two", "three")

for x, y in zip(first, second):
    print(x, y)

1 one
2 two
3 three

list(zip(*tables))

[(1, 2, 3, 4),
 (2, 4, 6, 8),
 (3, 6, 9, 12),
 (4, 8, 12, 16),
 (5, 10, 15, 20),
 (6, 12, 18, 24),
 (7, 14, 21, 28),
 (8, 16, 24, 32),
 (9, 18, 27, 36),
 (10, 20, 30, 40)]

a = [1, 2, 3, 4, 5]
b = second = ("one", "two", "three")

list(zip(a, b))

[(1, 'one'), (2, 'two'), (3, 'three')]

a = [1, 2, 3, 4, 5]
b = second = ("one", "two", "three")
c = ["I","II","III","IV"]

list(zip(a, b, c))

[(1, 'one', 'I'), (2, 'two', 'II'), (3, 'three', 'III')]

list(zip(*tables))

[(1, 2, 3, 4),
 (2, 4, 6, 8),
 (3, 6, 9, 12),
 (4, 8, 12, 16),
 (5, 10, 15, 20),
 (6, 12, 18, 24),
 (7, 14, 21, 28),
 (8, 16, 24, 32),
 (9, 18, 27, 36),
 (10, 20, 30, 40)]

*[1, 2, 3, 4] --> 1, 2, 3, 4,

zip(*[[1, 2, 3, 4, 5, 6, 7, 8, 9, 10],[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]])
zip([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [2, 4, 6, 8, 10, 12, 14, 16, 18, 20])

cylinder_volume(radius=1, height=4)

12.56

def foo(pos1, pos2,*args, **kwargs):
    print(pos1, pos2)
    print(args)
    print(kwargs)

foo("a","b", 1, 2, 3,4 , key1="val1",key2="val2" , key3="val3")

a b
(1, 2, 3, 4)
{'key1': 'val1', 'key2': 'val2', 'key3': 'val3'}

def make_contact(name, number, **customfields):
    contact = {"name":name, "phone":number}
    for key, value in customfields.items():
        contact[key] = value
    return contact

make_contact("vikrant", 9898540986, group="teacher", place="kudawale", profession="python trainer")

{'name': 'vikrant',
 'phone': 9898540986,
 'group': 'teacher',
 'place': 'kudawale',
 'profession': 'python trainer'}

make_contact("gunjan", 9898540986, group="friend", hostelblock="H", degree="B.E")

{'name': 'gunjan',
 'phone': 9898540986,
 'group': 'friend',
 'hostelblock': 'H',
 'degree': 'B.E'}

f = lambda x: x*x

f(5)

25

add3 = lambda x, y, z: x+y+z

add3(2, 3, 46)

51

records = [
    ("A", 34, 5.6),
    ("B", 30, 6.0), 
    ("C", 36, 5.8)
]

sorted(records, key= lambda r: r[1])

[('B', 30, 6.0), ('A', 34, 5.6), ('C', 36, 5.8)]

sorted(records, key= lambda r: r[2])

[('A', 34, 5.6), ('C', 36, 5.8), ('B', 30, 6.0)]

problems

• Write a function repeat which takeks function as argument and , initial value , n an integer. it repeated calling of function n times.

>>> repeat(lambda x: 2*x, 1, 5)
32

twice(twice(twice(twice(twice(1)))))

• Write a function compose which composed two functions

>>> f = lambda x:2*x
>>> g = lambda x:x*x
>>> fg = compose(f, g)
>>> fg(2) ## f(g(2))
8