String methods exercise | Python Fiddle

This_is_an_instance_of_a_string = "HeLlO wOrLd"

help(str.upper)
# mandatory arguments: 0
# type arguments: -
'''explanation: .upper returns a copy of a string in only uppercase
letters and thus changes the original string with both lower and
uppercase letters to only uppercase letters'''
# example with explanation above
print This_is_an_instance_of_a_string.upper()

help(str.title)
# mandatory arguments: 0
# type arguments: -
'''explanation: .title returns a copy of a string in which words start
with an uppercase letter, but all remaining letters are lowercase'''
# example with explanation above
print This_is_an_instance_of_a_string.title()

help(str.rfind)
# mandatory arguments: 1
# type arguments: variable with string element(s)
''' explanation: .rfind returns an integer which represents the last location or 
highest index of a certain subelement of the original string. This subelement 
must be specified in a variable and cannot be entered as an argument by itself. 
Optional arguments allow you to tell the method at which index to start or start 
and end looking. The method is case sensitive.'''
# example with explanation above
sub = "L"
# Here it finds the last "L" in "HeLlO wOrLd"
print This_is_an_instance_of_a_string.rfind(sub)
# Here it finds the first "L" in "HeLlO wOrLd"
print This_is_an_instance_of_a_string.rfind(sub,0,4)

help(str.startswith)
# mandatory arguments: 1
# type arguments: string
''' explanation: .startswith returns a boolean value after checking if the string starts
with a certain value as assigned in a variable. You can specifiy the
start and endposition where the method starts to compare with the string.
The method is case sensitive.'''
# example with explanation above
prefix = "w"
# Here it checks whether 'HeLlO wOrLd' starts with 'w'
print This_is_an_instance_of_a_string.startswith(prefix)
# Here it checks whether 'wOrLd' starts with 'w'
print This_is_an_instance_of_a_string.startswith(prefix,6)
# Here it checks whether 'wOrLd' starts with 'W'
prefixx = "W"
print This_is_an_instance_of_a_string.startswith(prefixx,6)

help(str.replace)
# mandatory arguments: 2
# type arguments: string
''' explanation: this returns a copy of the string where all occurrences of a variable
assigned a string value are replaced by a string value from a second
variable. With the count parapmeter, you can specify for which first
number of instances you want to use it. '''
# example with explanation above
old = "O"
new = "ooooo"
print This_is_an_instance_of_a_string.replace(old, new)
print This_is_an_instance_of_a_string.replace(old, new, 1)
print This_is_an_instance_of_a_string.replace(old, new, 2)

help(str.isalpha)
# mandatory arguments: 0
# type arguments: -
''' explanation: this returns a boolean value after checking if the string only contains
alphabetic characters, so letters '''
# example with explanation above
print This_is_an_instance_of_a_string.isalpha()
ALPstr = "Hello"
print ALPstr.isalpha()

Python Fiddle

Python Cloud IDE