Strings

A string is a sequence of characters. Python treats anything inside quotes as a string. This includes letters, numbers, and symbols. Python has no character data type so single character is a string of length 1.

s1 = "Hello"
s2 = 'wor'd'

print(s1,s2)

Multi line string

s = """I am Learning
Python String"""

print(s)

Accessing characters in Python String

s = "Hello World"

# Accesses first character: 'H'
print(s[0])  

# Accesses 5th character: 'o'
print(s[4])

print(s[-1])
print(s[-2])

String Slicing

Slicing is a way to extract portion of a string by specifying the start and end indexes. The syntax for slicing is string[start:end], where start starting index and end is stopping index (excluded).

s = "Hello World"

# Retrieves characters from index 1 to 3: 'ell'
print(s[1:4])  

# Retrieves characters from beginning to index 2: 'Hel'
print(s[:3])   

# Retrieves characters from index 3 to the end: 'lo World'
print(s[3:])   

# Reverse a string 'dlrow olleh'
print(s[::-1])

String Immutability

# Trying to change the first character raises an error
# s[0] = ''H"  # Uncommenting this line will cause a TypeError

# Instead, create a new string
s = "H" + s[1:]
print(s)

Sample Code

s = "hello world"

# Updating by creating a new string
s1 = "H" + s[1:]

# replacnig "world" with "pythonworld"
s2 = s.replace("world", "python world")

print(s1)
print(s2)

# Length of string
x = len(s)
print("length of s if ",x)

# Upper case
y = s.upper()
print("upper case: ",y)

# Lower case
z = s.lower()
print("lower case: ",z)

# remove empty spaces
str1 = "Hello w o r l d"
str2 = str1.strip()
print("strip: ",str2)

# Concat
str3 = str1 + " " + str2

# multiple
print(str1 * 3)

# find
s = "Hello World"
print("ello" in s)
print("HWH" in s)