Python Programming Made Easy (2016)

str1 = 'Hello World!'

str2 = "Python Programming"

print "str1[0]: ", str1[0]

print "str2[7:11]: ", str2[7:11]

str1 = 'Hello World!'

str2 = str1[:6] + 'Python'

print "Updated String :- ", str2

Backslash
notation

Description

\a

Bell or alert

\b

Backspace

\cx

Control-x

\C-x

Control-x

\e

Escape

\f

Formfeed

\M-\C-x

Meta-Control-x

\n

Newline

\nnn

Octal notation, where n is in the range 0.7

\r

Carriage return

\s

Space

\t

Tab

\v

Vertical tab

\x

Character x

\xnn

Hexadecimal notation, where n is in the range 0.9, a.f, or A.F

Operator

Description

Example

+

Concatenation - Adds values on either side of the operator

a + b results in HelloPython

*

Repetition - Creates new strings, concatenating multiple copies of the same string

a*2 results in HelloHello

[]

Slice - Gives the character from the given index

a[1] results in e

[ : ]

Range Slice - Gives the characters from the given range

a[1:4] results in ell

In

Membership - Returns true if a character exists in the given string

H in a results in 1

not in

Membership - Returns true if a character does not exist in the given string

M not in a results in 1

r/R

Raw 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 formatting

print "My name is %s and weight is %d kg!" % ('Tara', 50)

Format Symbol

Conversion

%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

SNo

Methods

Description

Example

1

capitalize()

Capitalizes first letter of string

str="hello python "

print str.capitalize()

Hello python

2

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

Computer".endswith("er")

True

3

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

str='Computer'

print str.find('put')

>>3

# On omitting the start parameters, the function starts the search from

# the beginning.

print str.find('put',2)

>>3

print str.find('put',1,3)

>> -1

# Displays -1 because the substring could not be found between the index 1 and 3-1

4

index(str, beg=0, end=len(string))

Same as find(), but raises an exception if str not found

"Computer".index('pat')

Traceback (most recent call last):

File "<pyshell#1>", line 1, in <module>

"Computer".index('pat')

ValueError: substring not found

5

isalnum()

Returns true if string has at least 1 character and all characters are alphanumeric and false otherwise

str='Hello Python'

print str.isalnum()

False

# The function returns False as space is an alphanumeric character.

print "Python123".isalnum()

True

6

isalpha()

Returns true if string has at least 1 character and all characters are alphabetic and false otherwise

print 'Python123'.isalpha()

False

print 'python'.isalpha()

True

7

isdigit()

Returns true if string contains only digits and false otherwise

str = '1234'

print str.isdigit()

True

8

islower()

Returns true if string has at least 1 cased character and all cased characters are in lowercase and false otherwise

print 'HELLO python'.islower()

hello python

9

isnumeric()

Returns true if a unicode string contains only numeric characters and false otherwise

str = u"year2013"

print str.isnumeric()

False

10

isspace()

Returns true if string contains only whitespace characters and false otherwise

str=' '

print str.isspace()

True

11

istitle()

Returns true if string is properly "titlecased" and false otherwise

print 'Hello World'.istitle()

True

12

isupper()

Returns true if string has at least one cased character and all cased characters are in uppercase and false otherwise

print "'HELLO python'.isupper()

True

13

join(seq)

Merges (concatenates) the string representations of elements in sequence seq into a string, with separator string

str1=('10', 'oct' ,'2013')

str="-"

print str.join(str1)

10-oct-2013

14

len(string)

Returns the length of the string

len("Computer")

8

15

lower()

Converts all uppercase letters in string to lowercase

"Optical Fibre".lower()

'optical fibre'

16

lstrip()

Removes all leading whitespace in string

" Python ".lstrip()

'Python '

17

max(str)

Returns the max alphabetical character from the string str

max("Python")

‘y’

18

min(str)

Returns the min alphabetical character from the string str

min("Python")

‘P’

19

replace(old, new [, max])

Replaces all occurrences of old in string with new or at most max occurrences if max given

"C++ is a powerful language".replace("C++","Python")

'Python is a powerful language'

20

rfind(str, beg=0,end=len(string))

Same as find(), but search backwards in string

"Python Program".rfind("P")

7

21

rindex( str, beg=0, end=len(string))

Same as index(), but search backwards in string

"Python Program".rindex("P")

7

22

rstrip()

Removes all trailing whitespace of string

" Python ".rstrip()

' Python'

23

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

"1:Anand-2:Babu-3:Charles-4:Dravid".split('-')

['1:Anand', '2:Babu', '3:Charles', '4:Dravid']

24

splitlines( num=string.count('\n'))

Splits string at all (or num) NEWLINEs and returns a list of each line with NEWLINEs removed

"1:Anu-\n2:Banu-\n3:Charles-\n4:David".splitlines(3)

['1:Anu-\n', '2:Banu-\n', '3:Charles-\n', '4:David']

25

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

"Python is a free software…….".startswith("Python")

True

26

strip([chars])

Performs both lstrip() and rstrip() on string

" Python ".strip()

'Python'

27

swapcase()

Inverts case for all letters in string

"python PROGRAMMING".swapcase()

'PYTHON programming'

28

title()

Returns "titlecased" version of string, that is, all words begin with uppercase and the rest are lowercase

"python PROGRAMMING".title()

'Python Programming'

29

upper()

Converts lowercase letters in string to uppercase

"python".upper()

'PYTHON'

30

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)

"1234".zfill(10)

'0000001234'

Constant

Description

Example

string.ascii_uppercase

The command displays a string containing uppercase characters.

>>> string.ascii_uppercase

'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

string.ascii_lowercase

The command displays a string containing all lowercase characters.

>>> string.ascii_lowercase

'abcdefghijklmnopqrstuvwxyz'

string.ascii_letters

The command displays a string containing both uppercase and lowercase characters.

>>> string.ascii_letters

'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

string.digits

The command displays a string containing digits.

>>> string.digits

'0123456789'

string.hexdigits

The command displays a string containing hexadecimal characters.

>>> string.hexdigits

'0123456789abcdefABCDEF'

string.octdigits

The command displays a string containing octal characters

>>> string.octdigits

'01234567'

string.punctuations

The command displays a string containing all the punctuation characters.

>>> string.punctuations

'!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}-'

string.whitespace

The command displays a string containing all ASCII characters that are considered

whitespace. This includes the characters space, tab, linefeed, return, formfeed, and vertical tab.

>>> string.whitespace

'\t\n\x0b\x0c\r '

string.printable

The command displays a string containing all characters which are considered printable like letters, digits, punctuations and whitespaces.

>>> string.printable

'0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!

"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}- \t\n\r\x0b\x0c'

Example 5.1: Write a program to check whether the string is a palindrome or not.

def palin():

str=input("Enter the String")

l=len(str)

p=l-1

index=0

while (index<p):

if(str[index]==str[p]):

index=index+1

p=p-1

else:

print "String is not a palindrome"

break

else:

print "String is a Palindrome"

Execution steps:

Fig 5.4: Palindrome execution steps

Output:

S.No

MetaCharacter

Usage

Example

1

[ ]

Used to match a set of characters

[star]

The regular expression

would match any of the

characters s, t , a or r.

[a-z]

The regular expression

would match only

lowercase characters.

2

^

Used to complementing a set of characters

[^star]

The regular expression

would match any other

characters than s, t , a or r.

3

$

Used to match the end of string only

Star$

The regular expression

would match Star in

BlueStar but will not match

Star in Stardom

4

*

Used to specify that the previous character can be matched zero or more times.

B*e

The regular expression

would match strings like

Bye, Blue, Bee and so on.

5

+

Used to specify that the previous character can be matched one or more times.

B+r

The regular expression would match strings like Beer, Baar and so on.

6

?

Used to specify that the previous character can be matched either

once or zero times

B?ar

The regular expression would only match strings like Bar or Bear

7

{ }

The curly brackets accept two integer value s. The first value

specifies the minimum no of occurrences and second value specifies the maximum of

occurrences

wate{1,4}r

The regular expression

would match only strings

water, wateer, wateeer or

wateeeer

Function

Description

re.compile()

compile the pattern into pattern objects. After the compilation the pattern objects will be able to access methods for various operations like searching and substitutions

re.match()

The match function is used to determine if the regular expression (RE) matches at the beginning of the string.

re.group()

The group function is used to return the string matched the RE

re.start()

The start function returns the starting position of the match.

re.end()

The end function returns the end position of the match.

re.span()

The span function returns the tuple containing the (start, end) positions of the match

re.search()

The search function traverses through the string and determines the position where the RE matches the string

re.findall()

The function determines all substrings where the RE matches, and returns them as a list.

re.finditer()

The function determines all substrings where the RE matches, and returns them as an iterator.

Example 5.2: Demonstration of re functions

import re

P=re.compile("hell*o")

m=re.match("hell*o", "hellooooo python")

print m.group()

m=re.match('hell*o', 'hellooooo python')

print m.start()

m=re.match('hell*o', 'hellooooo python')

print m.end()

m=re.match('hell*o', 'hellooooo python')

print m.span()

m=re.search('hell*o', 'hellooo python')

print m

m=re.findall('hell*o', 'hello helloo python')

print m