More String Methods

 Concepts

• Classification Methods
• isalpha()
• isdecimal()
• islower()
• isupper()
• isalnum()
• Case Conversion Methods
• capitalize()
• title()
• swapcase()
• Counting and Searching Methods
• count()
• index()
• rindex()
• find()
• rfind()

1. Classification Methods

These methods are used to check the characteristics of individual characters in a string.

1.1 Isalpha

Syntax:

str_var.isalpha()

Gives

True

if all the characters are alphabets. Otherwise,

False

Example 1:

Code

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is_alpha = "Rahul".isalpha()

print(is_alpha)

PYTHON

Output

True

Example 2:

Code

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is_alpha = "Rahul@123".isalpha()

print(is_alpha)

PYTHON

Output

False

1.2 Isdecimal

Syntax:

str_var.isdecimal()

Gives

True

if all the characters are decimals. Otherwise,

False

Example 1:

Code

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is_decimal = "9876543210".isdecimal()

print(is_decimal)

PYTHON

Output

True

Example 2:

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is_decimal = "123.R".isdecimal()

print(is_decimal)

PYTHON

Output

False

1.3 Islower

Syntax:

str_var.islower()

Gives

True

if all letters in the string are in lowercase. Otherwise,

False

Example 1:

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is_lower = "hello ravi!".islower()

print(is_lower)

PYTHON

Output

True

Example 2:

Code

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is_lower = "Hello Ravi!".islower()

print(is_lower)

PYTHON

Output

False

1.4 Isupper

Syntax:

str_var.isupper()

Gives

True

if all letters in the string are in uppercase. Otherwise,

False

Example 1:

Code

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is_upper = "HELLO RAVI!".isupper()

print(is_upper)

PYTHON

Output

True

Example 2:

Code

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is_upper = "hELLO rAVI!".isupper()

print(is_upper)

PYTHON

Output

False

1.5 Isalnum

Syntax:

str_var.isalnum()

Gives

True

if the string is alphanumeric (a letter or a number). Otherwise,

False

Example 1:

Code

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is_alnum = "Rahul123".isalnum()

print(is_alnum)

PYTHON

Output

True

Example 2:

Code

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is_alnum = "Rahul".isalnum()

print(is_alnum)

PYTHON

Output

True

Example 3:

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is_alnum = "Rahul@123".isalnum()

print(is_alnum)

PYTHON

Output

False

2. Case Conversion Methods

These methods are used to change the case of a string.

2.1 Capitalize

Syntax:

str_var.capitalize()

Gives a new string after converting the first letter in the string to uppercase and all other letters to lowercase.

Code

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capitalized = "the Planet Earth".capitalize()

print(capitalized)

PYTHON

Output

The planet earth

2.2 Title

Syntax:

str_var.title()

Gives a new string after converting the first letter of every word to uppercase.

If a word contains a number or a special character, the first letter after that is converted to uppercase.

Example 1:

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title_case = "the planet earth".title()

print(title_case)

PYTHON

Output

The Planet Earth

Example 2:

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title_case = "my_name#is john1doe and i love python".title()

print(title_case)

PYTHON

Output

My_Name#Is John1Doe And I Love Python

2.3 Swapcase

Syntax:

str_var.swapcase()

Gives a new string after converting the uppercase letters to lowercase and vice-versa.

Code

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swapped = "mY nAME IS rAVI".swapcase()

print(swapped)

PYTHON

Output

My Name is Ravi

3. Counting and Searching Methods

These methods are used to count the occurrences of a substring in a string and to find the position of a substring in a string.

3.1 Count

Syntax:

str_var.count(str, start_index, end_index)

Here, the

start_index

and the

end_index

are optional.

The

count()

method gives the number of times the specified string

str

appears in the string. It searches the complete string as default.

If

start_index

and

end_index

are provided, it searches between these indices. The

end_index

is not included.

Example 1:

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text = "Hello, world!"

letter_count = text.count("l")

print(letter_count)

 

PYTHON

Output

3

Example 2:

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text = "Hello, world!"

letter_count = text.count("l", 2, 10)

print(letter_count)

 

PYTHON

Output

2

3.2 Index

Syntax:

str_var.index(str, start_index, end_index)

Here, the

start_index

and the

end_index

are optional.

The

index()

method gives the index at the first occurrence of the specified string

str

.

It results in an error if the specified string

str

is not found.

The

index()

method searches the complete string as default. If

start_index

and

end_index

are provided, it searches between these indices. The

end_index

is not included.

Example 1:

Code

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text = "I have a spare key, if I lose my key"

word_index = text.index("key")

print(word_index)

 

PYTHON

Output

15

Example 2:

Code

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text = "coo coo"

word_index = text.index("co", 3, 6)

print(word_index)

PYTHON

Output

4

Example 3:

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text = "coo coo"

word_index = text.index("ha")

print(word_index)

PYTHON

Output

ValueError: substring not found

3.3 rIndex

Syntax:

str_var.rindex(str, start_index, end_index)

Here, the

start_index

and the

end_index

are optional.

The

rindex()

method gives the index at the last occurrence of the specified string

str

.

It results in an error if the specified string

str

is not found.

The

rindex()

method searches the complete string as default. If

start_index

and

end_index

are provided, it searches between these indices. The

end_index

is not included.

Example 1:

Code

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text = "I have a spare key, if I lose my key"

word_index = text.rindex("key")

print(word_index)

 

PYTHON

Output

33

Example 2:

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text = "coo coo coo"

word_index = text.rindex("co", 3, 10)

print(word_index)

PYTHON

Output

8

Example 3:

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text = "coo coo"

word_index = text.rindex("ha")

print(word_index)

PYTHON

Output

ValueError: substring not found

3.4 Find

Syntax:

str_var.find(str, start_index, end_index)

Here, the

start_index

and the

end_index

are optional.

The

find()

method gives the index at the first occurrence of the specified string

str

.

If the specified string

str

is not found, it returns

-1

.

The

find()

method searches the complete string as default. If

start_index

and

end_index

are provided, it searches between these indices. The

end_index

is not included.

It works similarly to the

index()

method. The only difference is that the

index()

method results in an error if the specified string is not found, while

find()

does not.

Example 1:

Code

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text = "I have a spare key, if I lose my key"

word_index = text.find("key")

print(word_index)

 

PYTHON

Output

15

Example 2:

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text = "coo coo"

word_index = text.find("co", 3, 6)

print(word_index)

PYTHON

Output

4

Example 3:

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text = "coo coo"

word_index = text.find("ha")

print(word_index)

PYTHON

Output

-1

3.5 rFind

Syntax:

str_var.rfind(str, start_index, end_index)

Here, the

start_index

and the

end_index

are optional.

The

rfind()

method gives the index at the last occurrence of the specified string

str

.

If the specified string

str

is not found, it returns

-1

.

The

rfind()

method searches the complete string as default. If

start_index

and

end_index

are provided, it searches between these indices. The

end_index

is not included.

It works similarly to the

rindex()

method. The only difference is that the

rindex()

method results in an error if the specified string is not found, while

rfind()

does not.

Example 1:

Code

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text = "I have a spare key, if I lose my key"

word_index = text.rfind("key")

print(word_index)

 

PYTHON

Output

33

Example 2:

Code

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text = "coo coo coo"

word_index = text.rfind("co", 3, 10)

print(word_index)

PYTHON

Output

8

Example 3:

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text = "coo coo"

word_index = text.rfind("ha")

print(word_index)

PYTHON

Output

-1