There are many in-built features APIs in python which we can use to process the given string. Following are a few examples.

Remove whitespace characters from a string

inputString = "Hello world!, How are you?"
finalString = ''.join(inputString.split())
print(finalString)

The split() function is used to separate the given string based on the delimiter. By default, the split() function uses the space as a delimiter.

In the above API, split and separate each character in the string by ignoring all the white spaces. Later join() function joins the output characters with empty characters to form a complete string without whitespace.

Remove characters from a string

input = "Hello world how are you?"

# Prints last 6 characters
outputString = input[:6]
print(outputString)

# Prints first 4 characters
print(input[:6])
print(outputString)

# Prints characters from 6th index to the 10th index
print(input[6:10])
print(outputString)

The above operations are known as slicing operations which are equivalent to the following

a[slice(start, stop, step)]

Slice has optional parameters i.e. you do not need to pass all three parameters. Not all objects need to be passed every time. Both of the following are accepted.

input[slice(stop)]
input[slice(start)]
input[slice(start, stop[, step])

The ":" represents the simple use of slicing which is equivalent to the slice() operation.

Convert lower case to upper case and vice-versa

inputString = "lowercasestring"
print(inputString.upper())

inputString1 = "UPPERCASESTRING"
print(inputString.lower())

Upper() is used to convert the lower case string to higher case whereas lower() is to convert characters from upper case to lower case.