AI Basics with AK

Season 02 - Introduction to Python Programming

Arun Koundinya Parasa

Episode 04

Strings & Characters - Part1

Agenda

• Strings
• String Mathematical Operations
• Indexing
• Slicing
• String Operations { Part2 }
• New Style Operators { Part2 }

Strings

var = "This is Python Learning Session"
type(var)

str

var1 = 'A'
type(var1)

str

print(len(var))
print(len(var1))

31
1

var + var1

'This is Python Learning SessionA'

var - var1

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-6ac0306cdaf6> in <cell line: 1>()
----> 1 var - var1

TypeError: unsupported operand type(s) for -: 'str' and 'str'

var * var1

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-6-057e19f0f1e8> in <cell line: 1>()
----> 1 var * var1

TypeError: can't multiply sequence by non-int of type 'str'

var2 = "This is sentence one.\nThis is sentence two.\nThis is sentence three"

print(var2)

This is sentence one.
This is sentence two.
This is sentence three

Strings

var3 =  '''
This is sentence one
This is sentence two
This is sentence three
'''
print(type(var3))
print("")
print(var3)

<class 'str'>


This is sentence one
This is sentence two
This is sentence three

var3 = r'This is sentence one.\nThis is sentence two.\nThis is sentence three'
print(type(var3))
print(var3)

<class 'str'>
This is sentence one.\nThis is sentence two.\nThis is sentence three

var4 = r'''This is sentence one.
This is sentence two.
This is sentence three
'''
print(type(var4))
print("")
print(var4)

<class 'str'>

This is sentence one.
This is sentence two.
This is sentence three

var = "Julius Caesar says, "Experience is the teacher of all things.""
print(var)

  File "<ipython-input-11-d472829db0e4>", line 1
    var = "Julius Caesar says, "Experience is the teacher of all things.""
                                ^
SyntaxError: invalid syntax

var = "Julius Caesar says, \"Experience is the teacher of all things.\""
print(var)

Julius Caesar says, "Experience is the teacher of all things."

var1 = "lets print blackslash \"
print(var1)

  File "<ipython-input-13-25f80e072a07>", line 1
    var1 = "lets print blackslash \"
           ^
SyntaxError: unterminated string literal (detected at line 1)

var1 = "lets print blackslash \\"
print(var1)

lets print blackslash \

var1 = "lets print blackslash \
second part of the sentence"
print(var1)

lets print blackslash second part of the sentence

String Mathematical Operations

print(var + "\n" +var1)

Julius Caesar says, "Experience is the teacher of all things."
lets print blackslash second part of the sentence

print(var * 2)

Julius Caesar says, "Experience is the teacher of all things."Julius Caesar says, "Experience is the teacher of all things."

print(var / 2)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-24-5d113b0a9ea4> in <cell line: 1>()
----> 1 print(var / 2)

TypeError: unsupported operand type(s) for /: 'str' and 'int'

var - "says"

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-29-927b51de5888> in <cell line: 1>()
----> 1 var - "says"

TypeError: unsupported operand type(s) for -: 'str' and 'str'

a = " Children"
b = " Played"
c = " and"

a + b + c + b

' Children Played and Played'

"Go "*2 +"before it's late"

"Go Go before it's late"

"First Name " "& Last Name"

'First Name & Last Name'

"First Name "*2 "& Last Name"

  File "<ipython-input-42-42675f58e5c5>", line 1
    "First Name "*2 "& Last Name"
                    ^
SyntaxError: invalid syntax

Indexing

var = "WORD"
print(var)

WORD

len(var)

4

print(var[0])
print(type(var[0]))
print(var[3])

W
<class 'str'>
D

var[4]

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-51-6e0795f01afe> in <cell line: 1>()
----> 1 var[4]

IndexError: string index out of range

var[-1]

'D'

var[-2]

'R'

var[-3]

'O'

var[-4]

'W'

var[-5]

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-56-8ea7679abd80> in <cell line: 1>()
----> 1 var[-5]

IndexError: string index out of range

Slicing

var = "Slice and Dice Me"
print(var)

Slice and Dice Me

var[0:5]

'Slice'

var[:5]

'Slice'

[: end ] specifies from the beginning to the end offset minus 1

var[6:9]

'and'

[ start : end ] indicates from the start offset to the end offset minus

var[10:]

'Dice Me'

[ start :] specifies from the start offset to the end.

var[10:-3]

'Dice'

var[10:-10]

''

var[0:6:2]

'Sie'

var[::-1]

'eM eciD dna ecilS'

var[::-1][3:7]

'eciD'

[ start : end : step ] extracts from the start offset to the end offset minus 1, skipping characters by step

var[3:-3:2]

'c n ie'

Thank You