If you are new to Python and you don’t know how to reverse a string in Python, here is a sample script using default reverse method [::-1]:
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print ("Enter a String") mystr = input() #reverse using [::-1] revstr = mystr[::-1] print ("Reverse is: "+revstr) |
The output of the above program:
Enter a String
superman
Reverse is: namrepus
So basically using [::-1], it is possible to reverse a string, but in interviews, sometimes to test your logical programming skill they may ask you to write a program to reverse a string without using the default reverse method.
The solution for the above question is to write a custom reverse() function in Python.
Here is the solution:
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def reverse(InputStr): #find the length of the string #then subtract by 1, because #we all know array starts with 0 i = len(InputStr) - 1 rev = '' #now loop through each character #and then store each character in #a new variable rev and return while i >= 0: rev = rev + str(InputStr[i]) i = i - 1 return rev #here is the usage of the above function print (reverse('spiderman')) |
The above code is well commented, read them to understand.
Are you a Python web developer?, you may need this script!!
This is the Python web script version of reversing a string without using default method:
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#!/usr/bin/python print "Content-type: text/html\n\n"; # Import modules for CGI handling import cgi, cgitb # Create instance of FieldStorage form = cgi.FieldStorage() #custom reverse function def reverse(InputStr): i = len(InputStr) - 1 rev = '' while i >= 0: rev = rev + str(InputStr[i]) i = i - 1 return rev #get the string from form and store it in mystring mystring = form.getvalue('string') print ''' <html> <body> <h3>Web Based Python script to Reverse a string without using default reverse method [::-1]</h3> <form action="" method="post"> <label>Enter a word or a sentence<label> <input type="text" name="string" /> <input type="submit" value="Submit" /> </form> </body> </html> ''' #print only if form is submitted if(mystring): print "<p>Reverse is: <strong>" + reverse(mystring) + "</strong></p>" |
The same custom reverse() function is used in the Python web script also, read the comments to understand the other features in the above script such is submitting a form, storing the form value in a variable, calling a function etc.,
And finally the demo of the web script,
