Page 268 - Computer Science Class 11 Without Functions
P. 268
>>> '+91-9898989898'.isdigit()
False
● s.isalnum(): A valid user name may be allowed to contain only alphabets and digits. The method isalnum()
enables us to check whether the username entered by a user comprises only alphabets and digits. For example,
>>> userId = 'Prodyot123'
>>> userId.isalnum()
True
>>> password = 'secret@123'
>>> password.isalnum()
False
Note that the first function call userId.isalnum() returns True as the string userId comprises only alphabets
and digits. However, password.isalnum() yields False as the string password includes a special character @.
● s.isspace(): The method isspace() returns True if the string comprises only whitespace characters and
False otherwise. For example,
>>> ' '.isspace()
True
>>> ' '.isspace()
True
>>> ' \t\n'.isspace()
True
>>> ' hello '.isspace()
False
>>> ''.isspace()
False
Note that the function call ''.isspace() yields False because the empty string does not contain even a single
whitespace.
● s.startswith(subStr): The method startswith(subStr) tests whether the string s starts with the string
subStr, passed as a parameter. For instance, in the following example, the first and second function calls returned
True and False, respectively, as 'unethical' starts with 'un' and not with 'ethical'.
>>> 'unethical'.startswith('un')
True
>>> 'unethical'.startswith('ethical')
False
>>> 'hello'.startswith('')
True
Note that the function call 'hello'.startswith('') yields True, because the null string is a prefix of every
string and the expression '' + 'hello' yields 'hello'.
● s.endswith(subStr): The method endswith(subStr) tests whether the string s ends with the suffix
subStr, passed as an argument. For example,.
>>> 'ethically'.endswith('ally')
True
>>> 'Bibasha Nayak'.endswith('Bibasha Nayak')
False
Note that in the function call 'Bibasha Nayak'.endswith('Bibasha Nayak') False, as the string
'Bibasha Nayak' contains an extra blank.
● s.find(subStr): The method find(subStr) searches for the first occurrence of the given string subStr in the
string s and returns the index of the first occurrence of the string passed as an argument. If the string subStr
does not appear anywhere in the string s, the method find() returns -1 indicating the condition substring not
found. For example,
>>> colors = 'green, red, blue, red, red, green'
>>> colors.find('red')
266 Touchpad Computer Science-XI

