Welcome to Day 11 of 100 Days of Python!

Almost every useful program works with text in some way.

Names, messages, usernames, sentences, file contents, commands, and even data received from users are commonly represented as strings in Python.

Today, we will learn:

• What strings are

• How to create strings

• Single and double quotes

• Using quotation marks inside strings

• Multiline strings

• Accessing individual characters using indexes

• String indexing and the IndexError

• Looping through a string using a for loop

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1. What is a String?

A string is a sequence of characters used to represent text.

In Python, strings are created by enclosing text inside quotation marks.

We can use:

• Single quotes ' '

• Double quotes " "

• Triple single quotes ''' '''

• Triple double quotes """ """

For example:

name = "Sritesh"

Here, "Sritesh" is a string.

We can also write:

name = 'Sritesh'

Both represent the same text.

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2. Creating a String

Let's create a simple string:

name = "Sritesh"

print(name)

Output:

Sritesh

We can also combine strings with other strings using the + operator.

name = "Sritesh"

print("Hello, " + name + "!")

Output:

Hello, Sritesh!

Here, the + operator joins the strings together. This is called string concatenation.

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3. Single Quotes vs Double Quotes

Python allows us to use either single or double quotation marks.

For example:

name1 = "Sritesh"
name2 = 'Sritesh'

print(name1)
print(name2)

Both produce:

Sritesh
Sritesh

So, in many situations, the choice between single and double quotes is simply a matter of style or convenience.

The important thing is to use matching quotation marks.

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4. Using Quotes Inside a String

Sometimes a sentence itself contains quotation marks.

For example:

He said, "I want to eat an apple".

If we try to write it using double quotes like this:

print("He said, "I want to eat an apple".")

Python cannot correctly determine where the string starts and ends.

One simple solution is to use single quotes around the entire string:

print('He said, "I want to eat an apple".')

Output:

He said, "I want to eat an apple".

This is one reason Python supporting both single and double quotes is convenient.

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5. Multiline Strings

Sometimes we need to store text that spans multiple lines.

Python allows us to create multiline strings using triple quotes.

For example:

message = """He said,
Hi Sritesh!
Hey! I am Good.
"I want to eat an apple."
"""

print(message)

Output:

He said,
Hi Sritesh!
Hey! I am Good.
"I want to eat an apple."

We can use either:

'''
multiple
lines
'''

or:

"""
multiple
lines
"""

for multiline string literals.

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6. Strings Are Sequences of Characters

A string is not treated as one indivisible piece of text.

Python stores it as a sequence of characters.

For example:

name = "Sritesh"

The string contains these characters:

S  r  i  t  e  s  h

Each character has a position called an index.

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7. String Indexing

Python uses zero-based indexing.

This means the first character has index 0, the second has index 1, and so on.

For:

name = "Sritesh"

the indexes are:

Character:  S   r   i   t   e   s   h
Index:      0   1   2   3   4   5   6

We can access a character using square brackets:

print(name[0])

Output:

S

Similarly:

print(name[1])

Output:

r

And:

print(name[2])

Output:

i

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8. Accessing Characters Individually

Let's access every character in "Sritesh":

name = "Sritesh"

print(name[0])
print(name[1])
print(name[2])
print(name[3])
print(name[4])
print(name[5])
print(name[6])

Output:

S
r
i
t
e
s
h

The important rule is:

String indexes start from 0.

So if a string contains 7 characters, the indexes are:

0 1 2 3 4 5 6

The last index is therefore length - 1.

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9. What Happens If the Index Does Not Exist?

Suppose we have:

name = "Sritesh"

There are only 7 characters, so the valid indexes are:

0 to 6

If we try:

print(name[7])

Python raises an error because index 7 does not exist.

The error is:

IndexError: string index out of range

For example:

name = "Sritesh"

print(name[7])

This will result in an IndexError.

So always make sure the index exists before trying to access a character.

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10. Looping Through a String

Because a string is a sequence of characters, we can use a for loop to process each character one by one.

Example:

name = "Sritesh"

for character in name:
    print(character)

Output:

S
r
i
t
e
s
h

The loop automatically goes through each character in the string.

The basic structure is:

for character in string:
    print(character)

Here, character is a loop variable that receives one character at a time.

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11. Looping Through a Multiline String

We can also loop through a multiline string.

For example:

message = """Hi Sritesh!
Hey! I am Good.
I am learning Python."""

for character in message:
    print(character)

The loop processes every character, including spaces and newline characters.

This is why the output may appear line by line when the original string contains multiple lines.

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12. Complete Program

Here is the program from today's practice:

name = "Sritesh"
friend = "Jyoti"
anotherFriend = "Rohit"

apple = '''He said,
Hi Sritesh!
Hey! I am Good.
"I want to eat an apple." '''

print("Hello, " + name + "!")
print(apple)

print(name[0])
print(name[1])
print(name[2])
print(name[3])
print(name[4])
print(name[5])
print(name[6])

print("Let's use a for loop\n")

for character in apple:
    print(character)

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13. Understanding the Program

Let's break the program into smaller parts.

Creating strings

name = "Sritesh"
friend = "Jyoti"
anotherFriend = "Rohit"

Three string variables are created.

Creating a multiline string

apple = '''He said,
Hi Sritesh!
Hey! I am Good.
"I want to eat an apple." '''

Triple single quotes allow the text to span multiple lines.

Concatenating strings

print("Hello, " + name + "!")

This joins:

"Hello, "

with:

"Sritesh"

and:

"!"

Result:

Hello, Sritesh!

Accessing characters

print(name[0])

Accesses the first character.

print(name[6])

Accesses the last character of "Sritesh".

Looping through characters

for character in apple:
    print(character)

This processes the multiline string character by character.

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14. Important String Concepts

Here are the main concepts from today's lesson:

Concept	Meaning
String	A sequence of characters representing text
'text'	String using single quotes
"text"	String using double quotes
'''text'''	Triple-quoted string
"""text"""	Triple-quoted string
+	Concatenates strings
string[index]	Accesses a character
Index 0	First character
for character in string	Iterates through characters
IndexError	Raised when a string index is out of range

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15. Quick Revision

Creating a string

name = "Sritesh"

Single quotes

name = 'Sritesh'

Concatenation

print("Hello, " + name)

Multiline string

message = """Line 1
Line 2
Line 3"""

Accessing a character

print(name[0])

Looping through a string

for character in name:
    print(character)

Remember zero-based indexing

For:

name = "Sritesh"

S → 0
r → 1
i → 2
t → 3
e → 4
s → 5
h → 6

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16. Key Takeaways

After completing Day 11, you should understand:

• What a string is in Python

• How to create strings using different quotation marks

• The difference between single and double quotes in terms of convenience

• How to include quotation marks inside strings

• How to create multiline strings

• That strings are sequences of characters

• How zero-based indexing works

• How to access individual characters

• Why an invalid index produces an IndexError

• How to loop through a string using a for loop

• How to concatenate strings using +

Strings are one of the most frequently used data types in Python. We will build on these fundamentals later when we learn string methods, slicing, formatting, and more advanced text processing.

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📂 Day 10 Resources

All notes and code for this day are available in the GitHub repository:

https://github.com/SriteshSuranjan/100-Days-of-Python/tree/main/11-Day11-Strings

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