Python Programming Strings

19 Apr 2022: Unit 3: Strings
PYTHON PROGRAMMING
B.Tech IV Sem CSE A

Today’s Topics
str class,
string inbuilt functions,
index[],
traversing string: for, while,
immutable strings,
string operators,
string operations

str class
 Strings are objects of the str class. We can create a string using
the constructor of str class.
The syntax of str() is:
 str(object, encoding='utf-8', errors='strict')
 object - The object whose string representation is to be
returned. If not provided, returns the empty string
 encoding - Encoding of the given object. Defaults of UTF-8
when not provided.
 errors - Response when decoding fails. Defaults to 'strict'.

str examples
name=str("Sreedhar")
age=str(24)
print(name)
print(age)
branch="computerscienceandengineering"
print(branch)
print(len(branch))
print(min(branch))
print(max(branch))
print(branch.center(40,'#'))
print(branch.find('science'))
Sreedhar
24
computerscienceandengineering
29
a
u
#####computerscienceandengineering######
8

print(branch.find('science',8,18))
print(branch.find('m',0,10))
print(branch.rfind('engine'))
print(branch.swapcase())
print(branch.startswith('science'))
print(branch.startswith('computer'))
print(branch)
print(branch.capitalize())
print(branch.upper())
8
2
18
COMPUTERSCIENCEANDENGINEERING
False
True
computerscienceandengineering
Computerscienceandengineering
COMPUTERSCIENCEANDENGINEERING

branches = 'cse, cst, csbs, ece'
branches.split()
branches.split(",") ['cse', ' cst', ' csbs', ' ece']
text = 'Binary Search'
print(text.rjust(20),"is a classic recursive algorithm")
text = 'Quick Search'
print(text.ljust(10),"is a classic recursive algorithm")
Binary Search is a classic recursive algorithm
Quick Search is a classic recursive algorithm

BASIC INBUILT PYTHON FUNCTIONS FOR
STRING
 len(a) #Return length i.e. number of characters in string a
 min(a) #Return smallest character present in a string
 max(a) #Return largest character present in a string

Index[ ] operator
 The indexing operator (Python uses square brackets to
enclose the index) selects a single character from a string,
characters are accessed by their position or index value.

index[] OPERATOR
a="Welcome to CSE4A students"
b=['Mango','per kg','value','is',204.14]
c=('Apple','per kg','value','is',103.24)
d=a[2]
print(d)
lastchar=a[-1]
print(lastchar)
print(b[2])
print(b[3-6])
print(b[-2])
print(c[0])
print(c[-1])
print(c[2-4])
print(b[7-8])
l
s
value
value
is
Apple
103.24
is
204.14

traversing string: for,while,
branch="Computer Science"
for char in branch:
print(char,end="")
string="Python Programming CSE4A"
j = 0
while j < len(string):
j += 1
print(string[0:j])

immutable strings
 Character sequences fall into two categories, i.e.
mutable and immutable.
 Mutable means changeable and immutable means
unchangeable.
 Strings are immutable sequences of characters.

String operators
branch="Computer Science and engineering"
print(branch[0])
print(branch[:3])
print(branch[2:6])
print(branch[4:])
print(branch[:])
print(branch[::-1])
print(branch[4::-1])
print(branch[0:16:2])
branch+=" !!"
print(branch)
C
Com
mput
uter Science and engineering
Computer Science and engineering
gnireenigne dna ecneicS retupmoC
upmoC
Cmue cec
Computer Science and engineering !!

college="G Pulla Reddy Engineering College"
branch="Computer Science and Engineering"
print(college+branch)
print(branch*2)
a="Engineering" in college
print(a)
b="JNTU" in college
print(b)
c="Maths" not in branch
print(c)
d="Science" not in branch
print(d)

G Pulla Reddy Engineering CollegeComputer Science and Engineering
Computer Science and EngineeringComputer Science and Engineering
True
False
True
False

string operations
 String Comparison
 String .format() Method()
 split() Method
 Testing String
 Searching Substring in a String
 Methods to Convert a String into Another String
 Stripping Unwanted Characters from a String
 Formatting String

branch1="Computer Science and Engineering"
branch2="Computer Science Technology"
print(branch1>branch2)
branch3="Computer Science Technology"
print(branch2==branch3)
print(branch2.split())
print(branch2.isalnum())
print(branch2.isalpha())
print(branch2.isdigit())
print(branch2.islower())
print(branch2.isupper())
print(branch2.isspace())
a="123test"
print(a.isalnum())
print(a.isalpha())
b="45678"
print(b.isdigit())
True
True
['Computer', 'Science', 'Technology']
False
False
False
False
False
False
True
False
True

course="G Pulla Reddy Engineering College"
print(course.endswith("College"))
print(course.startswith("Programming"))
print(course.find("Engineering"))
print(course.count("e"))
a="G Pulla Reddy Engineering Collegenntt"
print(a.rstrip())
True
False
14
5
G Pulla Reddy Engineering College

Python Programming Strings

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