Page 318 - Computer Science Class 11 With Functions
P. 318

●  On  execution  of  lines  11-13,  The  for-loop  looks  for  a  substring  of  length  lengthSubstr  that  matches  the  given
           substr.
        ● Line 13, if substr is found, the function returns True and False otherwise at line 14.

         Program 12.3 Searching for a substring in another string.

          01 def isSubString(string, substr):
          02     '''
          03     Objective: To search for a substring in given string
          04     Input Parameters:
          05       substr - string value
          06       string - string value
          07     Return value: True- if substr is present in string, False, otherwise
          08     '''
          09     substr, string = substr.lower(), string.lower()
          10     lengthSubstr = len(substr)
          11     for index in range(len(string)):
          12         if substr == string[index:index+lengthSubstr]:
          13             return True
          14     return False
        12.4.4 Constructing the Reverse of a Given String
        Let us develop a function reverseStr() that takes a string as an input parameter.
        ● Line 8, we initialize the string comprising characters in reverse order (revString) to an empty string.

        ● Line 9, we find the length of string (lengthSubstr).
        ●  On  execution  of  lines  10-11,  we  scan  the  string  and  append  every  subsequent  letter  to  the  beginning  of  the
           revString.
        ● On execution of line 12, finally, the function returns the reversed string (revString).

         Program 12.4 Constructing the reverse of a string.

          01 def reverseStr(string):
          02     '''
          03     Objective: To reverse the given string
          04     Input Parameters:
          05       string - string value
          06     Return value: reverseStr- reversed string
          07     '''
          08     revString = ''
          09     lengthSubstr = len(string)
          10     for char in string:
          11         revString = char + revString
          12     return revString
        On executing the Python module stringFns.py and invoking the appropriate functions, Python responded as
        follows:
         >>> distinct('Computer Science')
              'computer sin'
         >>> findCommon('Shekhar', 'Shayna')
              3
         >>> isSubString('Python programming', 'program')
              True
         >>> reverseStr('Python')
              'nohtyP'




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