Strings: Slicing, Membership, Built in Functions (count, find, capitalize, title, lower, upper and swap case, replace, join, isspace (), isdigit(), split(), startswith(), endswith())

A string is a sequence of characters enclosed within single quotes (' '), double quotes (" "), or triple quotes (''' ''' or """ """).

Example

name = "Python"
message = 'Hello World'

String Slicing

Slicing is used to extract a portion of a string.

Syntax

string[start:end:step]

Example

text = "Python Programming"

print(text[0:6])      # Python
print(text[7:18])     # Programming
print(text[:6])       # Python
print(text[::2])      # Pto rgamn
print(text[::-1])     # gnimmargorP nohtyP

Features

1. Start index is inclusive.
2. End index is exclusive.
3. Negative indexing is allowed.
4. Step value controls the interval.

Membership Operators in Strings

Membership operators check whether a character or substring exists in a string.

Operators

1. in
2. not in

Example

text = "Python"

print("Py" in text)       # True
print("Java" in text)     # False
print("Java" not in text) # True

Uses

1. Searching substrings.
2. Validation of user input.
3. Checking existence of characters.

Built in String Functions

1. count()

Returns the number of occurrences of a substring.

Syntax

string.count(substring)

Example

text = "banana"
print(text.count("a"))

Output

3

2. find()

Returns the index of the first occurrence of a substring.

Syntax

string.find(substring)

text = "Python Programming"
print(text.find("Pro"))

7

3. capitalize()

Converts the first character into uppercase and remaining characters into lowercase.

Example

text = "python programming"
print(text.capitalize())

Python programming

4. title()

Converts the first letter of each word into uppercase.

Example

text = "python programming language"
print(text.title())

Python Programming Language

5. lower()

Converts all characters to lowercase.

Example

text = "PYTHON"
print(text.lower())

python

6. upper()

Converts all characters to uppercase.

Example

text = "python"
print(text.upper())

PYTHON

7. swapcase()

Converts uppercase letters to lowercase and lowercase letters to uppercase.

Example

text = "PyThOn"
print(text.swapcase())

pYtHoN

8. replace()

Replaces a specified substring with another substring.

Syntax

string.replace(old, new)

text = "I like Java"
print(text.replace("Java", "Python"))

I like Python

9. join()

Joins elements of an iterable into a single string.

Syntax

separator.join(iterable)

words = ["Python", "is", "easy"]
print(" ".join(words))

Python is easy

10. isspace()

Returns True if all characters are whitespace characters.

Example

text = "   "
print(text.isspace())

True

11. isdigit()

Returns True if all characters are digits.

Example

text = "12345"
print(text.isdigit())

True

12. split()

Splits a string into a list.

Syntax

string.split(separator)

text = "Python,Java,C++"
print(text.split(","))

['Python', 'Java', 'C++']

13. startswith()

Checks whether a string starts with a specified value.

Example

text = "Python Programming"
print(text.startswith("Python"))

True

14. endswith()

Checks whether a string ends with a specified value.

Example

text = "Python Programming"
print(text.endswith("ming"))