. String Operations

# String can be made with both double and single quotes 
str1="Hello world"
str2 ='Hello World'

# if a string already contains single quote use double quote to enclose it and vice versa 
str1 ="Hello' World"
print(str1)

# Accessing string from index
str1 = "Hello World"
print("First char in string",str1[0]) # first index of the string
print("Last charecter in string",str1[-1]) # last index of the string

# Slicing a string( get char between 2nd and 7th index) 
print(str1[2:7])

# String are immutable in python 
str1[4]='a' # this will throw an error

# use triple quotes for multiline string
str1 ="""hello world 
python is the best programming language"""
print(str1)

#Compare two string
str1="Hello world"
str2="Python is best"
str3="Hello world"
print(str1==str2)
print(str1==str3)

# Concatenate two or more string
print(str1+' '+str2)

# loop through a string (below code will check if a is present in the string)
str1='python is a procedural programmin language'
for i in str1:
    if i=='a':
        print("a is present")
        break

str1="Hello world"
for idx,val in enumerate(str1):
    if val=='o':
        print("o is present",idx)

# get length of a string 
len(str1)

# Membership test(check if a particular charecter is present in the string or not)
print('a' in str1)
print('z' in str1)

# upper ,lower(),capitalize(),replace()
print(str1.upper())
print(str1.lower())
print(str1.capitalize())
print(str1.replace('a','z'))

# startswith(),isnumeric(),endswith(),islapha()
print(str1.startswith('pyth'))
print(str1.endswith('za'))
print(str1.isnumeric())
print('123'.isnumeric())
print('123'.isalpha())

#Exercise 1 - find out total numeric charecters in the below string
str1="World crude steel production for the 71 countries reporting to the World Steel Association (worldsteel) was 155.7 million tonnes (Mt) in April 2024, a 5.0% decrease compared to April 2023."
numeric_count=0
for i in str1:
    if i.isnumeric():
        numeric_count+=1
print("Total numeric values in string are ",numeric_count)

# Formatting string 
print(f"Total numeric values in string are {numeric_count}") # if we write f at the start of the string we can use the variables
# in curly braces

# raw format
print("hello python is \n best programming language") # notice a new line in the output due to \n
print(r"hello python is \n best programming language") # the new line will not be present now and \n will be printed as is 

# index of a char in string
str1.index('a') # return the first index of a char in a string

# remove extra spaces from start or end or both of a string
str1=" Hello world "
print(str1.lstrip())
print(str1.rstrip())
print(str1.strip())

# spillitng a string basis a special charecter
str1 ="apple, mango,banana,orange"
str1.split(',') # retruns a list type

# Exercise 2 split string on the basis of comma and remove spaces in each substring and print it 
str1 ="apple, mango,banana,orange"
for i in str1.split(','):
    print(i.strip())

# Reverse a string 
print(str1)
print(str1[::-1])

# Exercise 3 below string has fruit names seperated by comma , modify the string such that order of the fruits is reversed 
# but individual name of the fruit should remain same
str1 ="apple, mango,banana,orange"
new_String=''
for i in str1[::-1].split(','):
    new_String = new_String+','+i[::-1]
new_String=new_String[1:]
new_String

#Exercise 4 get last 3 charecter of a string 
str1[-3:]

#Exercise 4 get all charecters of a string after 4th index 
str1[4:]

# join() function in list of string (if you have a list of strings you can join then by a seperator as below)
str_list =["apple","mango","banana","orange"]
"|".join(str_list) # fruits will be replaced by our chosen charecter

# Chain string method
string = "   Hello, World!   "
string.strip().lower().replace("world", "Python")