Python Strings

What is a string in Python?

A string is an ordered sequence of text characters. It can contain letters, numbers, punctuation, spaces, Unicode characters, and emojis. Python does not have a separate character type, so one character is simply a string with length one.

Creating strings

Use matching single or double quotation marks. Choose the style that lets you include the other quote without unnecessary escaping:

single_quoted = 'Python'
double_quoted = "Programming"
with_apostrophe = "Python's syntax is readable"

print(single_quoted)
print(double_quoted)
print(with_apostrophe)
print(type(single_quoted))

Multiline strings

Triple single or double quotes create a string that can span multiple lines. They are useful for long text and documentation strings:

message = """Learning Python
is easier when examples
are clear and practical."""

print(message)

Important characteristics of strings

Accessing characters with indexes

Indexes start at zero from the left. Negative indexes count backward from the end, where -1 is the last character:

text = "Python"

print(text[0])
print(text[2])
print(text[-1])
print(text[-2])

An index outside the valid range raises IndexError. Indexes must be integers.

String slicing

Slicing extracts a range using the form text[start:stop:step]. The start index is included, but the stop index is excluded:

text = "Python"

print(text[1:4])   # characters at indexes 1, 2, and 3
print(text[:3])    # from the beginning
print(text[3:])    # from index 3 to the end
print(text[::2])   # every second character
print(text[::-1])  # reversed string

Strings are immutable

You cannot replace one character directly inside an existing string. Create a new string using slicing, concatenation, or a method such as replace():

message = "welcome learners"

# message[0] = "W"  # TypeError: strings cannot be changed in place
capitalized = "W" + message[1:]
updated = message.replace("learners", "Python developers")

print(capitalized)
print(updated)

Useful string operations

first = "Py"
second = "thon"

print(first + second)
print("ha" * 3)
print(len("Python"))

Common string methods

String methods do not modify the original string. They return a new value:

text = "  Learning Python is fun!  "

print(text.strip())
print(text.upper())
print(text.lower())
print(text.replace("fun", "useful"))
print("Python,Java,SQL".split(","))
print("-".join(["Python", "Java", "SQL"]))

strip() removes outer whitespace, upper() and lower() change case, replace() substitutes text, split() creates a list, and join() combines an iterable of strings.

Checking and searching text

text = "Python programming"

print(text.startswith("Python"))
print(text.endswith("ing"))
print(text.find("program"))
print(text.count("m"))
print(text.isalpha())
print("123".isdigit())

Methods such as startswith(), endswith(), find(), and count() help search text. Validation methods such as isalpha() and isdigit() inspect the contents of a string.

Concatenation and formatting

Use + for simple concatenation. For messages containing several values, f-strings are usually the clearest option:

name = "Asha"
age = 25
city = "Pune"

message = f"{name} is {age} years old and lives in {city}."
print(message)

The older format() method is still useful in existing code:

message = "{} works with {}.".format("Asha", "Python")
print(message)

Escape characters and raw strings

Escape sequences represent special characters inside a quoted string:

print("First line
Second line")
print("Column 1	Column 2")
print("She said, "Hello!"")
print("C:\Users\Asha")

A raw string treats backslashes mostly as ordinary characters, which is convenient for regular expressions and Windows-style paths:

path = r"C:UsersAsha
otes.txt"
print(path)

Testing membership

Use in and not in to check whether a character or substring exists:

text = "Python programming"

print("Python" in text)
print("Java" in text)
print("SQL" not in text)

Deleting a string name

You cannot delete one character from an immutable string, but del can remove the variable name from its namespace:

message = "Hello"
del message
# print(message)  # NameError: message is no longer defined

Best practices for Python strings

• Use clear quotation styles and escape quotes only when necessary.
• Remember that methods return new strings because strings are immutable.
• Use f-strings for readable messages that include variables.
• Use strip() and validation methods when processing user input.
• Use join() instead of repeatedly concatenating many strings in a loop.
• Use Unicode text directly in Python 3 and choose an explicit encoding when reading or writing files.