‘How to develop Pythonic coding rather than Python coding – Logic Perspective’

Online Workshop on ‘How to develop
Pythonic coding rather than Python
coding – Logic Perspective’
21.7.20 Day 1 session 2
Dr. S.Mohideen Badhusha
Professor/ CSE department
Alva’s Institute Engineering and
Technology
Mijar, Moodbidri, Mangalore
1

3
To acquire knowledge of iteration and string in Python
To comprehend the concept of looping statements in
Python
To practice the simple problems in iteration and string
Objectives of the Day 1 session 2

4
Iteration
for loop
for var in <collection>:
<statements>
where collection is iterable obj like list, tuple,dictionary,string
and range
a = [’i’, ’say’, ’hello’] # a list of string elements
for i in range(len(a)):
print (i,end=’ ’)
print (a[i])
Output
0 I
1 say
2 hello

5
Iteration
while loop
while condition :
<Statements>
i=0
while (i < 10):
print( i)
i += 1
o/p
0
1
2
.
9

6
Another Example for loop
for someChar in “Hello” :
print(someChar)
Output
H
e
l
l
o

7
d=[(1,'a'),(2,'b'),(3,'c'),(4,'d'),(5,'e')]
for (x, y) in d :
print (x,y)
o/p
1 a
2 b
3 c
4 d
5 e

8
for loop using range()
for x in range(5):
print x
o/p
0
1
2
3
4

9
Python program but not Pythonic
def traverse(string):
index = 0
while index < len(string):
letter = string[index]
print(letter)
index += 1
traverse('Monty Python')
Output ?

10
def traverse(string):
for letter in string:
print (letter)
traverse('Monty Python’)
Pythonic program

11
in operator
in is a boolean operator that checks
membership within a sequence
It is also called membership operator.
'a' in 'banana'
True
'o' in 'banana'
False

13
String handling functions
s=’HELLO’
s.lower() # hello
s1=’hello’
s1.upper() # HELLO
s.strip() -- returns a string with whitespace
removed from the start and end
s=’ I am happy ‘
s.strip() # I am happy ( no front and back spaces)
s.isalpha()# True
s.isdigit() # False
s.isspace() #False

14
split() and join() functions
s.split('delim') - returns a string into a list of
words separated by delim
Ex:
'aaa,bbb,ccc'.split(',') -> ['aaa', 'bbb', 'ccc'].
Defalut delim is space
s.join(list) -- opposite of split(), joins the
elements in the given list together using the
string as the delimiter.
Ex:
'---'.join(['aaa', 'bbb', 'ccc']) -> ‘aaa---bbb---ccc’
14

15
String Formatting Operator: %
The operator % allows strings to be built out of many
data items in a “fill in the blanks” fashion.
x = “Ram”
y = 34
print(“%s’s age is %d” % (x, y))
o/p
Ram’s age is 34
The tuple following the % operator is used to fill in
the blanks in the original string marked with %s %g
%d to represent string, float and integer values

16
Converting anything to a String
The built-in str() function can convert an
instance of any data type into a string
Ex:
print(“Hello ” + str(2))
o/p
Hello 2

17
Slicing strings
A segment of a string is called a slice.
Selecting a slice is similar to selecting a
character:
Ex:
s = 'Monty Python'
print(s[0:5])
Monty
print(s[6:12])
Python

18
String Indexing
print(s[:3])
o/p
Hel
print(s[3:])
o/p
lo
18

19
String Indexing
print(s[-1])
o/p
'o' #last char (1st from the end)
print(s[-4])
o/p
'e' # 4th from the end
print(s[:-3])
o/p
'He' – from starting, going up to but not
including the last 3 chars.
s[-3:] is 'llo' -- starting with the 3rd char from
the end and extending to the end of the string.

20
s[1:4] is 'ell' -- chars starting at index 1 and
extending up to but not including index 4
s[1:] is 'ello' -- omitting either index defaults
to the start or end of the string
s[:] is 'Hello' -- omitting both always gives
us a copy of the whole thing
s[1:100] is 'ello' -- an index that is too big is
truncated down to the string length

21
Concluding Tips
for loop in Python is entirely different from
other programming languages[ for var in
collection]
while loop in Python is similar to the
programming constructs in other languages
There is no do… while loop existing in Python
To be Pythonic, we should use data
structures and PEP 8 rules in Python
In slicing of string, st[i:n], we have to consider
from i th index to n-1 .
st[:n] from 0 th index to n-1.
st[i:] from i th index to end of the string

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