Course Ten - String & variables in python

String & variables in python

By ienex

Strings are one of the most commonly used data types in Python. They are easily created by enclosing characters in single (') or double (") quotes.

var1 = 'Hello World!'
var2 = "Python Programming"

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Accessing Values in Strings

In Python, characters are treated as strings of length one, so a single character is considered a substring. You can access substrings using square brackets []:

var1 = 'Hello World!'
var2 = "Python Programming"

print("var1[0]:", var1[0])
print("var2[1:5]:", var2[1:5])

Output:

var1[0]: H
var2[1:5]: ytho

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Updating Strings

Strings are immutable, so to update a string, you must assign a new value to the variable. You can also concatenate parts of the old string with a new string:

var1 = 'Hello World!'
print("Updated String:", var1[:6] + 'Python')

Output:

Updated String: Hello Python

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Escape Characters

Escape characters allow you to include non-printable characters or characters with special meaning in strings.

Escape	Hex	Description
\a	0x07	Bell / Alert
\b	0x08	Backspace
\cx	-	Control-x
\e	0x1b	Escape
\f	0x0c	Form feed
\n	0x0a	Newline
\r	0x0d	Carriage return
\s	0x20	Space
\t	0x09	Tab
\v	0x0b	Vertical tab
\xhh	-	Hexadecimal character

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String Operators

Assume:

a = 'Hello'
b = 'Python'

Operator	Description	Example
+	Concatenate strings	a + b → HelloPython
*	Repeat string	a * 2 → HelloHello
[]	Access character	a[1] → e
[:]	Slice substring	a[1:4] → ell
in	Membership test	'H' in a → True
not in	Not in string	'M' not in a → True
r/R	Raw string	r'\n' → prints \n
%	String formatting	See below

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String Formatting with %

Python supports C-style string formatting using %:

print("My name is %s and weight is %d kg!" % ('Zara', 21))

Output:

My name is Zara and weight is 21 kg!

Format Specifiers:

Symbol	Description
%c	Character
%s	String
%d	Integer
%i	Integer
%u	Unsigned integer
%o	Octal
%x	Hexadecimal (lowercase)
%X	Hexadecimal (uppercase)
%e	Exponential (lowercase e)
%E	Exponential (uppercase E)
%f	Floating-point
%g	Shorter of %f or %e
%G	Shorter of %f or %E

Additional formatting options:

Symbol	Function
*	Minimum width / precision
-	Left align
+	Show sign
<space>	Leading space for positive numbers
#	Add 0, 0x, or 0X for octal/hex
0	Pad with zeros
%%	Print % character

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Triple-Quoted Strings

Triple quotes allow multi-line strings including special characters like newlines \n or tabs \t:

para_str = """This is a long string
that spans multiple lines
and includes special characters like TAB (\t)
and newline (\n) characters."""
print(para_str)

Output:

This is a long string
that spans multiple lines
and includes special characters like TAB (    )
and newline 
 characters.

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Raw Strings

Raw strings ignore escape sequences, so backslashes are printed as-is:

print(r'C:\now')

Output:

C:\now

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