Python Tutorial
Python - Introduction Python - Syntax Python - Variable Python - Number Python - Casting Python - String Python - Operators Python - Conditions Python - Loops Python - List Python - Tuple Python - Set Python - Dictionary Python - Function Python - Module Python - Date & Time Python - Input Output Python - Error & Exception Python - File Handling
Python OOP
OOP - Introduction OOP - Class Members OOP - Constructor Destructor OOP - Data Hiding OOP - Inheritance OOP - Overriding OOP - Overloading

Python String

String literals in python are surrounded by either single quotation marks, or double quotation marks.

'hello' is the same as "hello"

Like many other popular programming languages, strings in Python are arrays of bytes representing unicode characters.

However, Python does not have a character data type, a single character is simply a string with a length of 1.

Square brackets can be used to access elements of the string.


Python Escape Character

Following table is a list of escape or non-printable characters that can be represented with backslash notation.

An escape character gets interpreted; in a single quoted as well as double quoted strings.

Backslash notation Hexadecimal character Description
\a 0x07 Bell or alert
\b 0x08 Backspace
\cx Control-x
\C-x Control-x
\e 0x1b Escape
\f 0x0c Form feed
\M-\C-x Meta-Control-x
\n 0x0a Newline
\nnn Octal notation, where n is in the range 0.7
\r 0x0d Carriage return
\s 0x20 Space
\t 0x09 Tab
\v 0x0b Vertical tab
\x Character x
\xnn Hexadecimal notation, where n is in the range 0.9, a.f, or A.F


Python String - Special Operators

Assume string variable a holds 'Hello' and variable b holds 'Python', then :

Operator Description Example
+ Concatenation - Adds values on either side of the operator a + b will give HelloPython
* Repetition - Creates new strings, concatenating multiple copies of the same string a*2 will give -HelloHello
[] Slice - Gives the character from the given index a[1] will give e
[ : ]Range Slice - Gives the characters from the given range a[1:4] will give ell
inMembership - Returns true if a character exists in the given stringH in a will give 1
not in Membership - Returns true if a character does not exist in the given string M not in a will give 1
r/RRaw String - Suppresses actual meaning of Escape characters. The syntax for raw strings is exactly the same as for normal strings with the exception of the raw string operator, the letter "r," which precedes the quotation marks. The "r" can be lowercase (r) or uppercase (R) and must be placed immediately preceding the first quote mark.print r'\n' prints \n and print R'\n'prints \n
%Format - Performs String formattingSee at next section

Python String - Formatting Operator

One of Python's coolest features is the string format operator %. This operator is unique to strings and makes up for the pack of having functions from C's printf() family. Following is a simple example:

Here is the list of complete set of symbols which can be used along with %:

Operator Description
%c character
%s string conversion via str() prior to formatting
%i signed decimal integer
%d signed decimal integer
%u unsigned decimal integer
%o octal integer
%x hexadecimal integer (lowercase letters)
%X hexadecimal integer (UPPERcase letters)
%e exponential notation (with lowercase 'e')
%E exponential notation (with UPPERCASE 'E')
%f floating point real number
%g the shorter of %f and %e
%G the shorter of %f and %E

Python Triple Quotes

Python's triple quotes comes to the rescue by allowing strings to span multiple lines, including NEWLINEs, TABs, and any other special characters.

The syntax for triple quotes consists of three consecutive single or double quotes.

Raw strings do not treat the backslash as a special character at all. Every character you put into a raw string stays the way you wrote it.


Python Built-in String Methods

Python includes the following built-in methods to manipulate strings:

Method Description
capitalize() Capitalizes first letter of string
center(width, fillchar) Returns a string padded with fillchar with the original string centered to a total of width columns.
count(str, beg = 0, end = len(string)) Counts how many times str occurs in string or in a substring of string if starting index beg and ending index end are given.
decode(encoding = 'UTF-8',errors = 'strict') Decodes the string using the codec registered for encoding. encoding defaults to the default string encoding.
encode(encoding = 'UTF-8',errors = 'strict') Returns encoded string version of string; on error, default is to raise a ValueError unless errors is given with 'ignore' or 'replace'.
endswith(suffix, beg = 0, end = len(string)) Determines if string or a substring of string (if starting index beg and ending index end are given) ends with suffix; returns true if so and false otherwise.
expandtabs(tabsize = 8) Expands tabs in string to multiple spaces; defaults to 8 spaces per tab if tabsize not provided.
find(str, beg = 0 end = len(string)) Determine if str occurs in string or in a substring of string if starting index beg and ending index end are given returns index if found and -1 otherwise.
index(str, beg = 0, end = len(string)) Same as find(), but raises an exception if str not found.
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 cased character and all cased characters are in lowercase and false otherwise.
isnumeric() Returns true if a unicode string contains only numeric characters and false otherwise.
isspace() Returns true if string contains only whitespace characters and false otherwise.
istitle() Returns true if string is properly "titlecased" and false otherwise.
isupper() Returns true if string has at least one cased character and all cased characters are in uppercase and false otherwise.
join(seq) Merges (concatenates) the string representations of elements in sequence seq into a string, with separator string.
len(string) Returns the length of the string
ljust(width[, fillchar]) Returns a space-padded string with the original string left-justified to a total of width columns.
lower() Converts all uppercase letters in string to lowercase.
lstrip() Removes all leading whitespace in string.
maketrans() Returns a translation table to be used in translate function.
max(str) Returns the max alphabetical character from the string str.
min(str) Returns the min alphabetical character from the string str.
replace(old, new [, max]) Replaces all occurrences of old in string with new or at most max occurrences if max given.
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() Removes all trailing whitespace of string.
split(str="", num=string.count(str)) Splits string according to delimiter str (space if not provided) and returns list of substrings; split into at most num substrings if given.
splitlines( num=string.count('\n')) Splits string at all (or num) NEWLINEs and returns a list of each line with NEWLINEs removed.
startswith(str, beg=0,end=len(string)) Determines if string or a substring of string (if starting index beg and ending index end are given) starts with substring str; returns true if so and false otherwise.
strip() Performs both lstrip() and rstrip() on string
swapcase() Inverts case for all letters in string.
title() Returns "titlecased" version of string, that is, all words begin with uppercase and the rest are lowercase.
translate(table, deletechars="") Translates string according to translation table str(256 chars), removing those in the del string.
upper() Converts lowercase letters in string to uppercase
zfill(width) Returns original string leftpadded with zeros to a total of width characters; intended for numbers, zfill() retains any sign given (less one zero).
isdecimal() Returns true if a unicode string contains only decimal characters and false otherwise.