Python – Strings

Python - Strings
Python - Strings

Python – Strings, Are amongst the maximum famous kinds in Python. We can create them clearly through enclosing characters in quotes. Python treats unmarried charges similar to double rates. Creating strings is as simple as assigning a fee to a variable. For instance −

var1 = 'Hello World!'
var2 = "Python Programming"

Python – Strings, Accessing Values in Strings

Python does no longer guide a individual kind; those are dealt with as strings of duration one, for that reason also taken into consideration a substring.

Python – Strings, To get entry to substrings, use the rectangular brackets for reducing along with the index or indices to acquire your substring. For instance −

#!/usr/bin/python

var1 = 'Hello World!'
var2 = "Python Programming"

print "var1[0]: ", var1[0]
print "var2[1:5]: ", var2[1:5]


Python – Strings, When the above code is executed, it produces the following result −

var1[0]:  H
var2[1:5]:  ytho

Updating Strings

You can “update” an existing string by way of (re)assigning a variable to every other string. The new value may be related to its preceding value or to a very exclusive string altogether. For instance −

#!/usr/bin/python

var1 = 'Hello World!'
print "Updated String :- ", var1[:6] + 'Python'

Python – Strings, When the above code is executed, it produces the following result −

Updated String :-  Hello Python

Python – Strings, Escape Characters

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

An break out individual gets interpreted; in a single quoted as well as double quoted strings.

Backslash notationHexadecimal characterDescription
\a0x07Bell or alert
\b0x08Backspace
\cxControl-x
\C-xControl-x
\e0x1bEscape
\f0x0cFormfeed
\M-\C-xMeta-Control-x
\n0x0aNewline
\nnnOctal notation, where n is in the range 0.7
\r0x0dCarriage return
\s0x20Space
\t0x09Tab
\v0x0bVertical tab
\xCharacter x
\xnnHexadecimal notation, where n is in the range 0.9, a.f, or A.F

String Special Operators

Assume string variable a holds ‘Hello’ and variable b holds ‘Python’, then −

Python - Strings

String Formatting Operator

One of Python’s coolest features is the string format operator %. This operator is particular to strings and makes up for the % of getting functions from C’s printf() family. Following is a simple example −

#!/usr/bin/python

print "My name is %s and weight is %d kg!" % ('Zara', 21)

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

My name is Zara and weight is 21 kg!

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

Format SymbolConversion
%ccharacter
%sstring conversion via str() prior to formatting
%isigned decimal integer
%dsigned decimal integer
%uunsigned decimal integer
%ooctal integer
%xhexadecimal integer (lowercase letters)
%Xhexadecimal integer (UPPERcase letters)
%eexponential notation (with lowercase ‘e’)
%Eexponential notation (with UPPERcase ‘E’)
%ffloating point real number
%gthe shorter of %f and %e
%Gthe shorter of %f and %E

Other supported symbols and functionality are listed in the following table −

SymbolFunctionality
*argument specifies width or precision
left justification
+display the sign
<sp>leave a blank space before a positive number
#add the octal leading zero ( ‘0’ ) or hexadecimal leading ‘0x’ or ‘0X’, depending on whether ‘x’ or ‘X’ were used.
0pad from left with zeros (instead of spaces)
%‘%%’ leaves you with a single literal ‘%’
(var)mapping variable (dictionary arguments)
m.n.m is the minimum total width and n is the number of digits to display after the decimal point (if appl.)

Triple Quotes

Python’s triple fees involves the rescue by permitting strings to span multiple strains, together with verbatim NEWLINEs, TABs, and any other unique characters.

The syntax for triple costs includes 3 consecutive single or double fees.

#!/usr/bin/python

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.
"""
print para_str

When the above code is executed, it produces the subsequent result. Note how each single special individual has been transformed to its published shape, proper down to the last NEWLINE at the quit of the string between the “up.” and final triple costs. Also observe that NEWLINEs arise both with an express carriage return at the give up of a line or its break out code (n) −

this is a long string that is made up of
several lines and non-printable characters such as
TAB (    ) and they will show up that way when displayed.
NEWLINEs within the string, whether explicitly given like
this within the brackets [
 ], or just a NEWLINE within
the variable assignment will also show up.

Raw strings do now not treat the backslash as a special man or woman in any respect. Every man or woman you put into a uncooked string remains the manner 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 might placed expression in r’expression’ as follows −

#!/usr/bin/python

print r'C:\\nowhere'

When the above code is finished, it produces the subsequent result −

C:\\nowhere

Python – Strings, Unicode String

Normal strings in Python are saved internally as 8-bit ASCII, while Unicode strings are saved as 16-bit Unicode. This lets in for a more various set of characters, which includes unique characters from maximum languages in the global. I’ll restriction my treatment of Unicode strings to the following −

#!/usr/bin/python

print u'Hello, world!'

When the above code is done, it produces the subsequent result −

Hello, world!

As you could see, Unicode strings use the prefix u, simply as raw strings use the prefix r.

Python – Strings, Built-in String Methods

Python consists of the subsequent integrated methods to govern strings −

Sr.No.Methods with Description
1capitalize()Capitalizes first letter of string
2center(width, fillchar)Returns a space-padded string with the original string centered to a total of width columns.
3count(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.
4decode(encoding=’UTF-8′,errors=’strict’)Decodes the string using the codec registered for encoding. encoding defaults to the default string encoding.
5encode(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’.
6endswith(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.
7expandtabs(tabsize=8)Expands tabs in string to multiple spaces; defaults to 8 spaces per tab if tabsize not provided.
8find(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.
9index(str, beg=0, end=len(string))Same as find(), but raises an exception if str not found.
10isalnum()Returns true if string has at least 1 character and all characters are alphanumeric and false otherwise.
11isalpha()Returns true if string has at least 1 character and all characters are alphabetic and false otherwise.
12isdigit()Returns true if string contains only digits and false otherwise.
13islower()Returns true if string has at least 1 cased character and all cased characters are in lowercase and false otherwise.
14isnumeric()Returns true if a unicode string contains only numeric characters and false otherwise.
15isspace()Returns true if string contains only whitespace characters and false otherwise.
16istitle()Returns true if string is properly “titlecased” and false otherwise.
17isupper()Returns true if string has at least one cased character and all cased characters are in uppercase and false otherwise.
18join(seq)Merges (concatenates) the string representations of elements in sequence seq into a string, with separator string.
19len(string)Returns the length of the string
20ljust(width[, fillchar])Returns a space-padded string with the original string left-justified to a total of width columns.
21lower()Converts all uppercase letters in string to lowercase.
22lstrip()Removes all leading whitespace in string.
23maketrans()Returns a translation table to be used in translate function.
24max(str)Returns the max alphabetical character from the string str.
25min(str)Returns the min alphabetical character from the string str.
26replace(old, new [, max])Replaces all occurrences of old in string with new or at most max occurrences if max given.
27rfind(str, beg=0,end=len(string))Same as find(), but search backwards in string.
28rindex( str, beg=0, end=len(string))Same as index(), but search backwards in string.
29rjust(width,[, fillchar])Returns a space-padded string with the original string right-justified to a total of width columns.
30rstrip()Removes all trailing whitespace of string.
31split(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.
32splitlines( num=string.count(‘\n’))Splits string at all (or num) NEWLINEs and returns a list of each line with NEWLINEs removed.
33startswith(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.
34strip([chars])Performs both lstrip() and rstrip() on string.
35swapcase()Inverts case for all letters in string.
36title()Returns “titlecased” version of string, that is, all words begin with uppercase and the rest are lowercase.
37translate(table, deletechars=””)Translates string according to translation table str(256 chars), removing those in the del string.
38upper()Converts lowercase letters in string to uppercase.
39zfill (width)Returns original string leftpadded with zeros to a total of width characters; intended for numbers, zfill() retains any sign given (less one zero).
40isdecimal()Returns true if a unicode string contains only decimal characters and false otherwise.