NCERT Solution - Strings, Computer Science (Python), Class 11 Notes - Class 11

Class 11: NCERT Solution - Strings, Computer Science (Python), Class 11 Notes - Class 11

The document NCERT Solution - Strings, Computer Science (Python), Class 11 Notes - Class 11 is a part of Class 11 category.
All you need of Class 11 at this link: Class 11

Very Short Answer type Questions [1 mark each] 

Question 1: Explain capitalize( ) method in Python. 

Answer: The method capitalize( ) returns a copy of the string with only its first character capitalized. 

Question 2: Write the syntax for capitalize( ) method. 

Answer: Following is the syntax for capitalize( ) method : str.capitalize( ) 

Question 3: What value will be returned by center (width, fillchar) method in Python 

Answer: width — This is the total width of the string, fillchar — This is the filler character 


Question 5: Describe the count(str, beg=0,end= len(string)) 

Answer: The method count( ) returns the number of occurrences of substring sub in the range [start, end]. 

Question 6: Describe the decode (encoding=’UTF8′, errors=’ strict’ ) 

Answer: The method decode( ) decodes the string using the codec registered for encoding. 

Question 7: What do you n .an by encode(encoding= ‘UTF- 8,errors=’strict’) 

Answer: The method encode( ) returns an encoded version of the string. Default encoding is the current default string encoding. 

Question 8: What do you mean by endswith(suffix, beg=0, end=len(string)) 

Answer: The method endswith( ) returns True if the string ends with the specified suffix, otherwise return False 

Question 9: Write the the syntax for find( ) method 

Answer: Following is the syntax for find( ) method : str.find(str, beg=0 end=len(string)) 

Question 10: Write the output of the following code.

print strl.find(str2,10); print strl.find(str2, 40); 

Answer: 15 15 -1 

Question 11: Write the syntax for isalnum( ) method. 

Answer: Following is the syntax for isalnum( ) method : str.isalnum( ) 

Question 12: Write the output of the following code. # !/usr/bin/python str = “this2009”; # No space in this string print str.isalnum( ); str = “this is string example….wow!!!”; print str.isalnum( ); 

Answer: True False 

Question 13: Write the syntax for isalpha( ) method. 

Answer: Following is the syntax for isalpha( ) method : str.isalpha( ) 

Question 14: Write the output of the following code. # !/usr/bin/python str = “this”; # No space & digit in this string print str.isalpha( ); str = “this is string example….wow!!!”; print str.isalpha( ); 

Answer: True False

Question 16: Why we use islower( ) method in python? 

Answer: The method islower( ) checks whether all the case-based characters (letters) of the string are lowercase 

Question 17: Describe the isspace( ) method 

Answer: The method isspace( ) checks whether the string consists of whitespace. 

Question 18: Write the output of the following code. #!/usr/bin/python str = ” “; print str.isspace( ); str = “This is string example….wow!!!”; print str.isspace( ); 

Answer: True False 

Question 19: Write the output of the following code. #!/usr/bin/python str = “this is string example….wow!!!”; print str.ljust(50, ‘0’); Answer: This is string example …wow!!!000000000000000000

Answer: str.upper() : Waltons Technology ….WOW!!! 

Question 21: Rectify the error (if any) in the given statements. >>>str = “Hello World” >>>str[5] = ‘p’ 

Answer: Strings are immutable. So convert to 2. list > > >s = list (str)’p’) >>s [5]=’p’ Question 22: Give the output of the following state-ments : >>>str = ‘Honesty is the best policy” >>>str.replace (‘o’.’*’) 

Answer: H*nesty is the best p*licy. 


Short Answer type Questions [2 mark each] 

Question 1: What do you mean by string in Python ? 

Answer: Strings are amongst the most popular types in Python. We can create them simply by characters in quotes. Python treats single quotes the same as double quotes. Creating strings is as simple as assigning a value to a variable. For example : var1 = ‘Waltons Technology!’ var2 = “Python Programming” 

Question 2: What is indexing in context to Python strings ? J Why is it also called two-way indexing ? 

Answer:

This is known as “two-way indexing”. 

NCERT Solution - Strings, Computer Science (Python), Class 11 Notes - Class 11

 A sub-part or a slice of a string, say s, can be obtained using s[n : m] where n and m are integers. Python returns all the characters at indices n, n+1, n+2,…. m-1. For example, ‘Oswaal Books’ [1 : 4] will give ‘swa’ 

Question 4: How you can “update” an existing string ? 

Answer: You can “update” an existing string by (re) assigning a variable to another string. The new value can be related to its previous value or to a completely different string altogether. Following is a simple example : # !/usr/bin/python var1 = ‘Hello World!’ print”Updated String:-“,var i[:6] + ‘Python’ 

Question 5: Describe Triple Quotes in Python. 

Answer: Python’s triple quotes comes to the rescue by allowing strings to span multiple lines, including verbatim NEWLINEs, TABs, and any other special characters. The syntax for triple quotes consists of three consecutive single or double quotes. # !/usr/bin/py thon para str = “””this is a long string that is made up of several lines and non-printable characters such as TAB ( \t ) and they will show up that way when displayed. NEWLINEs within the string, whether explicitly given like this within the brackets [ \n ], or just a NEWLINE within the variable assignment will also show up.


Answer: Raw strings don’t treat the backslash as a special character at all. Every character you put into a raw string stays in the way you wrote it : 

# !/usr/bin/python 

print ‘C:\\nowhere’ 

When the above code is executed, it produces the following result : 

C:\nowhere Now let’s make use of raw string. 

We would put expression in r’expression’ as follows : 

# !/usr/bin/python 

print r’C:\\nowhere’ When the above code is executed, it produces the following result : C:\\nowhere 

Question 7: Explain Unicode String with example. 

Answer: Normal strings in Python are stored internally as 8-bit ASCII, while Unicode strings are stored as 16- bit Unicode. This allows for a more varied set of characters, including special characters from most languages in the world. 

Example……. 

#!/usr/bin/python print u’Hello, world!’ 

Question 8: Describe isdecimal( ) with example. Answer: The method isdecimal( ) checks whether the string consists of only decimal characters. This method is present only on Unicode objects. 

Note : To define a string as Unicode, one simply prefixes a ‘u’ to the opening quotation mark of the assignment. Below is the example. 

Syntax :

Answer: The method zfill( ) pads string on the left with zeros to fill width. 

Syntax : str.zfill(width) 

Parameters: This is final width of the string. This is the width which we would get after filling zeros. 

Return Value: This method returns padded string 

Question 10: Write the output of the following code 

# !/usr/bin/python str = “this is string example….wow!!!”; 

print str.zfill(40);

 print str.zfill(50); 

Answer: On compiling and running the above program, this will produce the following result : OOOOOOOOthis is string example….wow!!! 000000000000000000this is string example…. wow!!! 

Question 11: Write the output of the following code 

# !/usr/bin/python from string import maketrAns. 

# Required to call maketrAns. function. intab = “aeiou” outtab = “12345” trantab = maketrAns.(intab, outtab) str = “this is string example….wow!!!”; print str.trAns.late(trantab, ‘xm’);

 Answer: The given code will produce following result : th3s 3s str3ng 21pl2….w4w!M 

Question 12: Describe the following method trans.late(table, deletechars=””) 

Answer: The method translate( ) returns a copy of the string in which all characters have been translated using table (constructed with the maketrans( ) function in the string module), optionally deleting all characters found in the string deletechars.

str = “this is string example….wow!!!”; 

print str.title( ); On compile and run the above program, this will produce the following result : This Is String Example….Wow!!! 

Question 14: Give an example of swapcase( ) in Python 

Answer: The following example shows the usage of swapcase( ) method. 

# !/usr/bin/py thon str = “this is string example….wow!!!”; print str.swapcase( ); str = “THIS IS STRING EXAMPLE….WOW!!!”; 

print str.swapcase( ); 

This will produce the following result : 

THIS IS STRING EXAMPLE….WOW!!! this is string example….wow!!! 

Question 15: Define strip ([chars]) with its syntax 

Answer: The method strip( ) returns a copy of the string in which all chars have been stripped from the beginning and the end of the string (default whitespace characters). Syntax: str.strip([chars]); 

Question 16: Explain Parameters of str.startswith(str, beg=0,end=len( string) ); 

Answer: str — This is the string to be checked. 

beg — This is the optional parameter to set start index of the matching boundary. 

end — This is the optional parameter to set end index of the matching boundary.

Question 18: Write the output of the given Python code 

# !/usr/bin/python str = “this is really a string example…. wow!!!”; 

str = “is”; print str.rfind(str); 

print str.rfind(str, 0,10); 

print str.rfind(str, 10, 0); 

print str.find(str); 

print str.find(str, 0,10); 

print str.find(str, 10, 0); 

Answer: Above code will produce the following result : 5 5 -1 2 2 -1 

Question 19: Write the output of the given code 

#!/usr/bin/python str = “this-is-real-string-example….wow!!!”; 

print “Min character: ” + min(str); 

str = “this-is-a-string-example….wow!!!”; 

print “Min character: ” + min(str); 

Answer: Min character: ! Min character: ! 

Question 20: Write the output of the given code #!/usr/bin/python str = “this is really a string example….wow!!!”;

Max character: y Max character: x 

Question 21: Describe the function maketrans( ) 

Answer: The method maketrans( ) returns a translation table that maps each character in the intab string into the character at the same position in the outtab string. Then this table is passed to the translate( ) function. 

Syntax : str.maketrans(intab, outtab]); 

Question 22: Write the output of the following code #!/usr/bin/py thon str = ” this is string example….wow!!! “; 

print str.lstrip( ); 

str = “88888888this is string example….wow!!!8888888”; 

print str.lstrip(‘8’); 

Answer: Output this is string example….wow!!! this is string example..,.wow!!!8888888 Question 23: Study the given script defmetasearch( ): import re p=re.compile(‘sing+’) searchl=re.search(p,’ Some singers sing well’) if searchl: match=searchl.group( ) index=searchl.start( ) lindex=search 1 ,end( ) print “matched”, match, “at index”, index ,”ending at”, lindex else:

The output would be “N match found” Justification : re.search( ) rill attempt the pattern throughout the string, i ntil it finds a match. re.match( ) on the other hand, only attempts the pattern at the very start of the string. 

Example : >>>re.match(“d”, “abcdef’) # No match >>>re.search(“d”, “abcdef’) # Match 

Question 24: What will be the output of the script mentioned below? Justify your answer, def find) ): import re p=re.compile(‘ sing+’) searchl=p.findall(‘Some singer sing well’) print searchl 

Answer: Output : [‘sing’, ‘sing’] Justification : fmdall( ) finds all occurences of the given substring with metacharacter. 


Long Answer type Questions [4 mark each]

 Question 1: What is the concept of immutable strings ? 

Answer: Strings are immutable means that the contents of string cannot be chrnged after it is created. 

For example : >>> str = ‘Meney’ >>> str [3] = ‘h’ Type Error : ‘str’ object not support item assignment Python does not allow to change a character in a string. 

So an attempt to replace ‘e’ in the string by ‘h’ displays a Type Error.

 Question 2: What do you understand by traversing a string ? 

Ans. Traversing a string means accessing all the elements of the string one after the other by using the subscript. A string can be traversed using for loop or while loop.

i = i + 1 Output : P y t h o n 

Question 3: Write a program to check whether the string is a palindrome or not. 

Answer: def palindrom ( ) : str = input (“Enter the string”) l = len (str) P = l – 1 inex = 0 while (index < p) : 

if (str[index] = = str [p]): 

index = index + 1 p = p-1 else : 

print “String is not a palindrom” break else : 

print “String is a palindrom” 

Question 4: Write a program to count number of ‘s’ in the string ‘successor’. 

Answer: def letcount ( ) : word = ‘successor’ count = 0 for letter in word :  

Write a program to determine if the given word is present in the string. 

Answer: def wsearch ( ) : imprt re word = ‘good’ search1 = re.search (word, ‘I am a good person’) 

if search1 : position = search1.start ( ) print “matched”, word, “at position”, position 

else : print “No match found” 

Question 6: Input a string “Green Revolution”. Write a script to print the string in reverse. Answer: def reverseorder(list 1) : relist = [ ] i = len (list 1) -1 while i > = 0 : relist.append (list [i]) i = 1 -1 return relist 

Question 7: Write a program to print the pyramid ? 

Answer: num = eval (raw_input (“Enter an integer from 1 to 5:”)) 

if num < 6 : for i in range (1, num + 1): for j in range (num-i, 0,-1): print (” “) for j in range (i, 0, -1): print (j)

Output :

NCERT Solution - Strings, Computer Science (Python), Class 11 Notes - Class 11

 Question 8: Write the syntax of isdecimal( ) and give suitable example 

Answer: The method isdecimal( ) checks whether the string consists of only decimal characters. This method are present only on Unicode objects. Below is the example. 

Syntax str.isdecimal( ) 

Example 

# !/usr/bin/python str = u”this2009″; 

print str.isdecimal( ); 

str = u”23443434″; 

print str.isdecimal( );

This will produce the following result : False True 

Question 9: Write the output of the following python code #!/usr/bin/python str = “Line1-a b c d e f\nLine2- a b c\n\nLine4- a b c d”; 

print str.splitlines( ); 

print str.splitlines(O); 

print str.splitlines(3); 

print str.splitlines(4);

[‘Linel-a b c d e f\ri, ‘Line2- a b c\ri, ‘\n’, ‘Line4- a b c d’] [‘Linel-a b c d e f\n’, ‘Line2- a b c\ri, ‘\ri, ‘Line4- a b c d’] [‘Linel-a b c d e f\ri, ‘Line2- a b c\ri, ‘\n’, ‘Line4- a bed’] 

Question 10: Define split( ) with suitable example.

 Answer: The method split( ) returns a list of all the words in the string, using str as the separator (splits on all whitespace if left unspecified), optionally limiting the number of splits to num. Syntax str.split(str=””, num=string.count(str)). 

Parameters str — This is any delimeter, by default it is space. 

num — This is number of lines to be made. 

Example # !/usr/bin/python str = “Linel-abcdef \nLine2-abc \nLine4-abcd”; 

print str.split( ); 

print str.split(‘ 1 ); 

OUTPUT [‘Linel-abcdef’, ‘Line2-abc’, ‘Line4-abcd’] [‘Linel-abcdef’, ‘\nLine2-abc \nLine4-abcd’] 

Question 11: Explain replace(old, new [, max]) 

Answer: The method replace( ) returns a copy of the string in which the occurrences of old have been replaced with new, optionally restricting the number of replacements to max. Syntax str.replace(old, new[, max]) 

Parameters – old — This is old substring to be replaced. 

new — This is new substring, which would replace old substring. 

max — If this optional argument max is given, only the first count occurrences are

OUTPUT thwas was string example….wow!!! thwas was really string thwas was string example….wow!!! thwas is really string 

Question 12: Describe index(str, beg=0, end=len(string)) with example 

Answer: The method index( ) determines if string str occurs in string or in a substring of string if starting indexbeg and ending index end are given. This method is same as find( ), but raises an exception if sub is not found. Syntax str.index(str, beg=0 end=len(string)) Example # !/usr/bin/python str = “this is string example….wow!!!”; 

str = “exam”; 

print str.index(str); print str.index(str, 10); 

print str.index(str, 40); 

OUTPUT 15 15 

Traceback (most recent call last): 

File “test.py”, line 8, in print str.index(str, 40); 

ValueError: substring not found shell returned 1 

Question 13: Explain expandtabs(tabsize=8) with example 

Answer: The method expandtabs( ) returns a copy of the string in which tab characters ie. ‘\t’ have been expanded using spaces, optionally using the given tabsize (default 8).

print “Original string: ” + str; 

print “Defualt exapanded tab: ” + str.expandtabs( ); 

print “Double exapanded tab: ” + str. expandtabs(16); 

OUTPUT Original string: this is string example….wow!!! 

Defualt exapanded tab: this is string example…. wow!!! 

Double exapanded tab: this is string example…. wow!!! 

Question 14: Write Python script that takes a string with multiple words and then capitalizes the first letter of each word and forms a new string out of it. 

Answer: string = raw_input (“Enter a string :”) 

length = len (string) a = 0 end – length string 2 = ” 

# empty string while a < length if a == 0 string 2 += string [0].upper() a += 1 elif (string [a] = = ‘ ‘ and string [a+1) !=”) : string 2 + = string [a] string 2 + = string [a+l].upper( ) a + = 2 else : string 2 + = string [a] a + = 1 print “Original string :”, string print “Converted string :”, string2

length = len (string) max length = 0 max sub = ‘ ‘ sub = ‘ ‘ lensub = 0 for a in range (length) :

 if string [a] in aeiou ‘or string [a] in’AEIOU’:

 if lensub > maxlength : maxsub = sub maxlength – lensub sub = ‘ ‘ lensub 0 else : sub += string[a] lensub = len(sub) a + = 1 

print “Maximum length consonent substring is :”, maxsub,

 print “with”, maxlength, “characters” 

Question 16: Write a program that reads email id of a person in the form of a string and ensures that it belongs to domain @gmail.com. 

Answer: email = raw_input (“Enter email ID :”) 

domain = “@gmail.com” lendo = len(domain) 

lenm = len(email) sub = email [lenm – lendo:] 

if sub = = domain : if lendo ! = lenm : 

print “It is a valid email ID” else :

Write a program that reads a string and then prints a string that capitalizes every other letter in the string. 

Answer: string = raw_input (“Enter a string:”) 

length = len (string) string2 = ” ” for a in range (0, length, 2): 

string 2 + – string [a] if a < (length-1): 

string 2+ = string [a+1],upper() 

print “Original string is”, string print “Converted string is”, string2 

Question 18: Consider the string str=”Global Warming” Write statements in Python to implement the following 

(a) To display the last four characters. 

(b) To display the substring starting from index 4 and ending at index 8. 

(c) To check whether string has alphanu-meric characters or not 

(d) To trim the last four characters from the string. 

(e) To trim the first four characters from the string. 

(f) To display the starting index for the substring „ WaD. 

(g) To change the case of the given string. 

(h) To check if the string is in title case. 

(i) To replace all the occurrences of letter „aD in the string with „*? 

Answer: (a) print str[-4:] (b) print str[4:8] (c) str.isalnum( ) (d) str[:-4] (g) str.swapcase( ) (h) str.istitle( ) (i) str.replace(‘a’,’*’)

NCERT Solution - Strings, Computer Science (Python), Class 11 Notes - Class 11

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