String Data Type


A string is an ordered set of characters represented either in single or double quotes. A string can contain alphabets, digits and special characters.

Python doesn’t support character data type instead a single character is considered as a string of length 1.

The indexing of a string with length n starts from 0 to n-1.

An escape or non-printable character is represented with backslash (\) in strings.

String handling in python is a simple and easy task as we have various built-in functions and operators.

In python, the operator + (plus sign) is a concatenation operator and the operator * (asterisk) is the repetition operator.

We can print the subset of a string by using the slice operator ( [ ] or [ : ] ) with index starting at 0.

Example

    str1 = “Tutorials”
    str2 = “Duniya”
    print str1		        # Prints complete string
    print str1[5]		# Prints 5th character of the string
    print str1[2:7]		# Prints characters starting from 2nd to 7th
    print str1[4: ]		# Prints complete string starting from 4th character
    print str2 * 3		# Prints string 2 times
    print str1 + str2	        # Prints concatenation of str1 and str2    


Output:

    Tutorials
    i
    torial
    rials
    DuniyaDuniya
    TutorialsDuniya    


We can update the whole string but can’t update a particular character within a string.

Example:

    myStr = “Tutorials”
    myStr[1] = “A”	        # An error will occur as a particular character can’t be updated
    myStr = “Duniya”	# whole string can be updated
    print(myStr)		# prints Duniya    



Python built-in string functions

Function name Description
capitalize() Returns a copy of the string only with its first character capitalized.
count(string,begin,end) Returns the number of occurrences of a substring in a string.
endswith(suffix, beg=0, end=len(string) Returns a boolean value if the string terminates with given suffix between begin and end.
expandtabs(tabsize=8) Returns a copy of the string in which tab characters i.e. '\t' are expanded using spaces, optionally using the given tabsize (default 8).
find(substring, beginIndex, endIndex) Returns the index value of the string where substring is found between begin index and end index.
format(value) Returns a formatted version of S using the passed value.
isalnum() Returns true if string has at least 1 character and all characters are alphanumeric and false otherwise.
isalpha() Returns true if string has at least 1 character and all characters are alphabetic and false otherwise.
isdigit() Returns true if string contains only digits and false otherwise.
islower() Returns true if string has at least 1 character and all characters are in lowercase and false otherwise.
isupper() Returns true if string has at least 1 character and all characters are in uppercase and false otherwise.
isnumeric() Returns true if a string contains only numeric characters and false otherwise.
isdecimal() Returns true if all the characters of the string are decimals otherwise false.
isspace() Returns true if string contains only whitespace characters and false otherwise.
istitle() Returns true if the string is titled properly and false otherwise. A title string is the one in which the first character is uppercase and other characters are lowercase.
isidentifier() Returns true if the string is a valid identifier otherwise false.
join(seq) Returns a string which is the concatenation of the strings in the sequence seq.
len(string) Returns the length of the string.
lower() Returns a copy of the string in which all characters have been lowercased.
upper() Returns a copy of the string in which all characters have been uppercased.
lstrip() Returns a copy of the string in which all chars have been stripped from the beginning of the string.
replace(old, new [,count]) Returns a copy of the string in which the occurrences of old have been replaced with new, optionally restricting the number of replacements to count.
rfind(str, beg=0,end=len(string)) Same as find(), but search backwards in string.
rindex( str, beg=0, end=len(string)) Same as index(), but search backwards in string.
rjust(width,[, fillchar]) Returns a space-padded string with the original string right-justified to a total of width columns.
rstrip() Returns a copy of the string in which all chars have been stripped from the end of the string (default whitespace characters).
split(str="", num=string.count(str)) 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.
startswith(str, beg=0,end=len(string)) Returns true if string starts with str otherwise false.
splitlines( num=string.count('\n')) Returns a list with all the lines in string, optionally including the line breaks, if num is supplied.
strip([chars]) Returns a copy of the string in which all chars have been stripped from the beginning and the end of the string.
swapcase() Returns a copy of the string in which all the case-based characters have had their case swapped.
title() Returns a copy of the string in which first characters of all the words are capitalized.
translate(table, deletechars=””) Returns a copy of the string in which all characters have been translated using table, optionally deleting all characters found in the string deletechars.
zfill(width) Returns original string leftpadded with zeros to a total of width characters.