String Flashcards
complete String- with functions
str1=’Python’
str1[0]
> > >
P
str1= ‘Python’
str1[2+3]
»>
n
What is Slicing in string and its Syntax?
Extracting a substring from a string
Syntax: string[start:end:step]
str1=’python’
print(str1[-5:-1])
Output
YTHO
str1=’python’
print(str1[-1:-4])
Output
’’
str1=’python’
print(str1[:-5:-1])
NOHT
Mutable Object
If the value of an object can be changed after it is created, It is called mutable object
Example
Lists, Set and dictionaries.
Immutable Object
If the value of an object cannot be changed after it is created, it is called immutable object
Example
Numeric, String and Tuple
String is Immutable
A string is an immutable data type. It means that the value (content) of a string object cannot be changed
after it has been created. An attempt to do this would lead to an error.
Example
»> str1 = ‘Python’
»> str1[1]=’Y’
TypeError
Concatenation
Operator : +
»> str1 = “Python”
»> str2 = “Programming”
»> str1 + str2
‘PythonProgramming’
Repetition
Use : To repeat the given string multiple times.
Repetition operator : *
»> str1 = “Hello “
»> str1*5
‘Hello Hello Hello Hello Hello’
Membership
Membership is the process of checking whether a particular character or substring is present in a sequence
or not. It is done using the ‘in’ and ‘not in’ operators.
Example
»> str1 = “Programming in Python”
> > > “Prog” in str1“ming in”
in str1“Pyth “ in str1“Pyth “
not in str1
True
True
False
True
String Functions
len()
Returns the length of the given string
»> str1 = ‘Hello World!’
»> len(str1)
12
capitalize()
converts the first character of a string to capital
(uppercase) letter and rest in lowercase.
str1 = “python Programming for
11th”
str1.capitalize()
‘Python programming for 11th’
title()
converts the first letter of every word in the string
in uppercase and rest in lowercase
»> str1 = “python ProGramming
for 11th”
»> str1.title()
‘Python Programming For 11th’
lower()
Returns the string with all uppercase letters
converted to lowercase
»> str1 = “PYTHON PROGRAMMING for
11th”
»> str1.lower()
‘python programming for 11th’
upper()
Returns the string with all lowercase letters
converted to uppercase
»> str1 = “python programming
for 11th”
»> str1.upper()
‘PYTHON PROGRAMMING FOR 11TH’
count()
Returns number of times a substring occurs in the
given string
»> str1 = “python programming for
11th”
»> str1.count(“p”)
2
»> str1.count(“pyth”)
1
find()
Returns the index of the first occurrence of
substring in the given string. If the substring is
not found, it returns -1
»> str1 = “python programming
for 11th”
»> str1.find(‘r’)
8
»> str1.find(‘u’)
-1
index()
Same as find() but raises an exception if the
substring is not present in the given string
»> str1 = “python programming for
11th”
»> str1.index(‘r’)
8
»> str1.index(‘u’)
ValueError: substring not found
isalnum()
The isalnum() method returns True if all
characters in the string are alphanumeric (either
alphabets or numbers). If not, it returns False.
»> str1 = ‘HelloWorld’
»> str1.isalnum()
True
»> str1 = ‘HelloWorld2’
»> str1.isalnum()
True
isalpha()
Returns True if all characters in the string are
alphabets, Otherwise, It returns False
»> ‘Python’.isalpha()
True
»> ‘Python 123’.isalpha()
False
isdigit()
returns True if all characters in the string are
digits, Otherwise, It returns False
»> ‘1234’.isdigit()
True
»> ‘123 567’.isdigit()
False
isspace()
Returns True if has characters and all of them are
white spaces (blank, tab, newline)
»> str1 = ‘ \n \t’
»> str1.isspace()
True
»> str1 = ‘Hello \n’
»> str1.isspace()
False
islower()
returns True if the string has letters all of them
are in lower case and otherwise False.
»> str1 = ‘hello world!’
»> str1.islower()
True
»> str1 = ‘hello 1234’
»> str1.islower()
True
»> str1 = ‘hello ??’
»> str1.islower()
True
isupper()
returns True if the string has letters all of them are
in upper case and otherwise False.
»> str1 = ‘HELLO WORLD!’
»> str1.isupper()
True
»> str1 = ‘HELLO 1234’
»> str1.isupper()
True
»> str1 = ‘HELLO ??’
»> str1.isupper()
True
strip()
Returns the string after removing the whitespaces
both on the left and the right of the string
»> str1 = ‘ Hello World! ‘
»> str1.strip()
‘Hello World!’
lstrip()
Returns the string after removing the whitespaces
only on the left of the string
»> str1 = ‘ Hello World! ‘
»> str1.lstrip()
‘Hello World! ‘
rstrip()
Returns the string after removing the whitespaces
only on the right of the string
»> str1 = ‘ Hello World! ‘
»> str1.rstrip()
’ Hello World!’
replace(oldstr,newstr)
used to replace a particular substring in a string
with another substring
»> str1 = ‘Hello World!’
»> str1.replace(‘o’,’*’)
‘Hell* W*rld!’
partition()
The partition() function is used to split a string
into three parts based on a specified separator.
»> str1 = ‘India is a Great Country’
»> str1.partition(‘is’)
(‘India ‘, ‘is’, ‘ a Great Country’)
»> str1.partition(‘are’)
(‘India is a Great Country’,’ ‘,’ ‘)
split()
Returns a list of words delimited by the specified
substring. If no delimiter is given then words are
separated by space.
»> str1 = ‘India is a Great Country’
»> str1.split()
[‘India’,’is’,’a’,’Great’, ‘Country’]
»> str1 = ‘India is a Great Country’
»> str1.split(‘a’)
[‘Indi’, ‘ is ‘, ‘ Gre’, ‘t Country’]
startswith()
startswith() function is used to check whether a
given string starts with a particular substring.
endswith()
endswith() function is used to check whether a
given string ends with a particular substring.
str = “Python Programming
Language”
print(str.startswith(“Pyt”))
print(str.startswith(“Pyth”))
print(str.endswith(“age”))
print(str.endswith(“uage”))
print(str.startswith(“Pyts”))
Output
True
True
True
True
False
join()
str.join(sequence)
returns a string in which the string elements of
sequence have been joined by str separator. if few
of the members of the sequence are not string, error
is generated.
»> ‘-‘.join(‘Python’)
‘P-y-t-h-o-n’
»> ‘-
‘.join([‘Ajay’,’Abhay’,’Alok’])
‘Ajay-Abhay-Alok’
»> ‘*-
*‘.join([‘Ajay’,’Abhay’,123])
TypeError: sequence item 2:
expected str instance, int found
