Python Strings and strings types with Examples

Python Strings
1. Slicing Strings
2. Modify Strings
3. Concatenate Strings
4. Format Strings
5. Escape Strings
Prof. Kartiki Deshmukh

•Strings in python are surrounded by either single quotation
marks, or double quotation marks.
•'hello' is the same as "hello".
•You can display a string literal with the print() function.
You can use double or single quotes:
print("Hello")
print('Hello')
Output:
Hello
Hello

Quotes Inside Quotes
You can use quotes inside a string, as long as they don't
match the quotes surrounding the string.
print("It's alright")
print("He is called 'Johnny'")
print('He is called "Johnny"')
Output:
It's alright
He is called 'Johnny'
He is called "Johnny"

Assign String to a Variable
Assigning a string to a variable is done with the variable name
followed by an equal sign and the string.
a = "Hello"
print(a)
Output:
Hello

Multiline Strings
You can assign a multiline string to a variable by using
three quotes.
a = """Modern College
of arts, science and commerce,
Shivajinagar, Pune"""
print(a)
Output:
Modern College
of arts, science and commerce,
Shivajinagar, Pune Prof. Kartiki Deshmukh

Strings are Arrays
•Like many other popular programming languages, strings
in Python are arrays of bytes representing unicode
characters.
•However, Python does not have a character data type, a
single character is simply a string with a length of 1.
•Square brackets can be used to access elements of the
string.
a = "Hello, World!"
print(a[1])
Output:
e

Looping Through a String
Since strings are arrays, we can loop through the
characters in a string, with a for loop.
for x in ‘mango’:
print(x)
Output:
m
a
n
g
o

String Length
To get the length of a string, use the len() function.
a = "Hello, World!"
print(len(a))
Output:
13

Check String
To check if a certain phrase or character is present in a string,
we can use the keyword in.
txt = "The best things in life are free!"
print("free" in txt)
Output:
True

Use it in an if statement:
if "free" in txt:
print("Yes, 'free' is present.")
Output:
Yes, 'free' is present.

Check if NOT
To check if a certain phrase or character is NOT present in
a string, we can use the keyword not in.
print("expensive" not in txt)
Output:
True

Slicing Strings
You can return a range of characters by using the slice
syntax.
Specify the start index and the end index, separated by a
colon, to return a part of the string.
b = "Hello, World!"
print(b[2:5])
Output:
llo

Slice From the Start
By leaving out the start index, the range will start at the
first character.
b = "Hello, World!"
print(b[:5])
Output:
Hello

Slice To the End
By leaving out the end index, the range will go to the end.
b = "Hello, World!"
print(b[2:])
llo, World!

Negative Indexing
Use negative indexes to start the slice from the end of
the string.
b = "Hello, World!"
print(b[-5:-2])
Output:
orl
Note: From: "o" in "World!" (position -5)
To, but not included: "d" in "World!" (position -2)

Modify Strings
1. Upper Case
The upper() method returns the string in upper case.
a = "Hello, World!"
print(a.upper())
Output:
HELLO, WORLD!

2. Lower Case
The lower() method returns the string in lower case.
a = "Hello, World!"
print(a.lower())
Output:
hello, world!

3. Remove Whitespace
Whitespace is the space before and/or after the actual
text, and very often you want to remove this space.
The strip() method removes any whitespace from the
beginning or the end.
a = " Hello, World! "
print(a.strip())
Output:
Hello, World!

4. Replace String
The replace() method replaces a string with another string.
a = "Hello, World!"
print(a.replace("H", "J"))
Output:
Jello, World!

5. Split String
The split() method returns a list where the text
between the specified separator becomes the list
items.
a = "Hello, World!"
print(a.split(","))
Output:
['Hello', ' World!']

String Concatenation
To concatenate, or combine, two strings you can use the +
operator.
a = "Hello"
b = "World"
c = a + b
print(c)
Output:
HelloWorld
To add a space between them, add a " “.
a = "Hello"
b = "World"
c = a + " " + b
print(c)
Output:
Hello World

Format Strings
As we learned in the Python Variables chapter, we
cannot combine strings and numbers, but we can
combine strings and numbers by using f-strings or
the format() method.
To specify a string as an f-string, simply put an f in front
of the string literal, and add curly brackets {} as
placeholders for variables and other operations.

age = 36
txt = f"My name is John, I am {age}"
print(txt)
Output:
My name is John, I am 36

Placeholders and Modifiers
A placeholder can contain variables, operations, functions,
and modifiers to format the value.
price = 59
txt = f"The price is {price} dollars"
print(txt)
Output:
The price is 59 dollars

A placeholder can include a modifier to format the value.
A modifier is included by adding a colon : followed by a
legal formatting type, like .2f which means fixed point
number with 2 decimals.
price = 59
txt = f"The price is {price:.2f} dollars"
print(txt)
Output:
The price is 59.00 dollars

A placeholder can contain Python code, like math
operations.
txt = f"The price is {20 * 59} dollars"
print(txt)
Output:
The price is 1180 dollars

Escape Characters
To insert characters that are illegal in a string, use an escape
character.
An escape character is a backslash followed by the
character you want to insert.
The escape character allows you to use double quotes when
you normally would not be allowed.
txt = "We are the so-called "Vikings" from the north.“
Output:
We are the so-called "Vikings" from the north.

Code Result
' Single Quote
Backslash
n New Line
r Carriage Return
t Tab
b Backspace
f Form Feed
ooo Octal value
xhh Hex value
Escape Characters
Other escape characters used in Python.

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