Some Commonly Used String Methods

count(): Returns the number of times a specified value occurs in a string
startswith(): Returns true if the string starts with the specified value
endswith(): Returns true if the string ends with the specified value	Form validation of an email ID
isalpha(): Returns True if all characters in the string are in the alphabet	Usage: Form validation
isdigit(): Returns True if all characters in the string are digits	Usage: Form validation
isspace(): Returns True if all characters in the string are whitespaces	Usage: Form validation
islower(): Returns True if all characters in the string are lower case isupper(): Returns True if all characters in the string are upper case
lower(): Converts a string into lower case upper(): Converts a string into upper case	Used in palindrome check.
split(): Splits the string at the specified separator, and returns a list	Usage: File processing
splitlines(): Splits the string at line breaks and returns a list	Usage: File processing
strip(): Returns a trimmed version of the string
zfill(): Fills the string with a specified number of 0 values at the beginning	Left padding a string with 0s (ex. phn no)

A more exhaustive list

Method	Description
capitalize()	Converts the first character to upper case
casefold()	Converts string into lower case
center()	Returns a centered string
count()	Returns the number of times a specified value occurs in a string
encode()	Returns an encoded version of the string
endswith()	Returns true if the string ends with the specified value
expandtabs()	Sets the tab size of the string
find()	Searches the string for a specified value and returns the position of where it was found
format()	Formats specified values in a string
format_map()	Formats specified values in a string
index()	Searches the string for a specified value and returns the position of where it was found
isalnum()	Returns True if all characters in the string are alphanumeric
isalpha()	Returns True if all characters in the string are in the alphabet
isascii()	Returns True if all characters in the string are ascii characters
isdecimal()	Returns True if all characters in the string are decimals
isdigit()	Returns True if all characters in the string are digits
isidentifier()	Returns True if the string is an identifier
islower()	Returns True if all characters in the string are lower case
isnumeric()	Returns True if all characters in the string are numeric
isprintable()	Returns True if all characters in the string are printable
isspace()	Returns True if all characters in the string are whitespaces
istitle()	Returns True if the string follows the rules of a title
isupper()	Returns True if all characters in the string are upper case
join()	Converts the elements of an iterable into a string
ljust()	Returns a left justified version of the string
lower()	Converts a string into lower case
lstrip()	Returns a left trim version of the string
maketrans()	Returns a translation table to be used in translations
partition()	Returns a tuple where the string is parted into three parts
replace()	Returns a string where a specified value is replaced with a specified value
rfind()	Searches the string for a specified value and returns the last position of where it was found
rindex()	Searches the string for a specified value and returns the last position of where it was found
rjust()	Returns a right justified version of the string
rpartition()	Returns a tuple where the string is parted into three parts
rsplit()	Splits the string at the specified separator, and returns a list
rstrip()	Returns a right trim version of the string
split()	Splits the string at the specified separator, and returns a list
splitlines()	Splits the string at line breaks and returns a list
startswith()	Returns true if the string starts with the specified value
strip()	Returns a trimmed version of the string
swapcase()	Swaps cases, lower case becomes upper case and vice versa
title()	Converts the first character of each word to upper case
translate()	Returns a translated string
upper()	Converts a string into upper case
zfill()	Fills the string with a specified number of 0 values at the beginning

Count of each alphabet

for i in string.ascii_letters: print(i, x.count(i))

a 39

b 6

c 21

d 11

e 71

f 6

g 15

h 27

i 31

j 1

k 3

l 27

m 6

n 40

o 32

p 10

q 4

r 31

s 37

t 59

u 13

v 3

w 6

x 1

y 12

z 1

A 2

B 0

C 0

D 0

E 0

F 0

G 0

H 0

I 1

J 0

K 0

L 1

M 0

N 1

O 1

P 5

Q 0

R 1

S 2

T 1

U 0

V 0

W 0

X 0

Y 0

Z 0

Count of characters, count of words and count of sentences in a given string

x = "A line about Python String from the book 'Pg 191, Learning Python (O'Reilly, 5e)': Strictly speaking, Python strings are categorized as immutable sequences, meaning that the characters they contain have a left-to-right positional order and that they cannot be changed in place. In fact, strings are the first representative of the larger class of objects called sequences that we will study here. Pay special attention to the sequence operations introduced in this post, because they will work the same on other sequence types we’ll explore later, such as lists and tuples. Note: All string methods returns new values. They do not change the original string."

print(len(x))

print(len(x.split())) # it by default splits on space

print(len(x.split("."))) # this splits the string on full stop

658

105

split()

Date of birth:

23-07-2023 -> extract date or month or year

20/07/2023 -> extract date or month or year

20 Jun 2023 -> extract date or month or year

05.01.2015 -> extract date or month or year

5.1.2015 (do it using date formatting)

Way 1: slice[]

Way 2: split()

Way 3: Date Formatting

d = dateutil.parser.parse("5.1.2015", dayfirst=True)

Find first occurence of ‘that’, and find all occurences of the word ‘that’

x.find('that') # This gives you the starting index of first occurence

165

print(x[x.find('that') : x.find('that') + 15])

that the charac

pattern = 'that'

for match in re.finditer(pattern, x):

s = match.start()

e = match.end()

# print('String match "%s" at slice %d:%d' % (x[s:e], s, e))

print('String match "{}" at slice {}:{}'.format(x[s:e], s, e))

String match "that" at slice 165:169

String match "that" at slice 240:244

String match "that" at slice 372:376

Find first occurence of ‘in’, and find all occurences of the word ‘in’

Startswith() and Endswith()

# How to check if a phone number is from a particular country?

# Condition for a number to come from a particular country is it’s starting country code

print('+917651179969'.startswith('+91')) # India

print('+917651179969'.startswith('+92')) # Pakistan

print('+17644479969'.startswith('+1)) # US and Canada

True

False

True

# How to check if a person’s DOB is from 2003? Assuming that DOB is following a pattern...

dates_of_birth = ['01/01/2003', '02/01/2004', '07/07/2003',

'03/02/2003', '04/03/2004', '05/03/2004']

for i in dates_of_birth:

if i.endswith('2003'): print(i)

Split and SplitLines

# split()
string = 'Jack Smith Junior is a good boy'
string.split()
# splitlines()
string2 = """Jack Smith Junior is a good boy
He loves programming"""
string2.splitlines()

Note About String in Python

A line about Python String from the book "Pg 191, Learning Python (O'Reilly, 5e)":
Strictly speaking, Python strings are categorized as immutable sequences, meaning that the characters they contain have a left-to-right positional order and that they cannot be changed in place. In fact, strings are the first representative of the larger class of objects called sequences that we will study here. Pay special attention to the sequence operations introduced in this post, because they will work the same on other sequence types we’ll explore later, such as lists and tuples.
Note: All string methods returns new values. They do not change the original string.

Now in code

In [4]:

import string
import re
import random

In [5]:

string.ascii_lowercase

Out[5]:

'abcdefghijklmnopqrstuvwxyz'

In [6]:

l = [chr(i) for i in range(ord('a'), ord('z') + 1)]

In [7]:

print(l)

['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

In [8]:

s = ""
for i in range(ord('a'), ord('z') + 1): s += chr(i)
print(s)

abcdefghijklmnopqrstuvwxyz

In [9]:

print(string.digits)
print(string.ascii_lowercase)
print(string.ascii_uppercase)
print(string.ascii_letters)
print(string.printable)
print(string.hexdigits)
print(string.octdigits)

0123456789
abcdefghijklmnopqrstuvwxyz
ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~ 	

0123456789abcdefABCDEF
01234567

In [10]:

x = "A line about Python String from the book 'Pg 191, Learning Python (O'Reilly, 5e)': Strictly speaking, Python strings are categorized as immutable sequences, meaning that the characters they contain have a left-to-right positional order and that they cannot be changed in place. In fact, strings are the first representative of the larger class of objects called sequences that we will study here. Pay special attention to the sequence operations introduced in this post, because they will work the same on other sequence types we’ll explore later, such as lists and tuples. Note: All string methods returns new values. They do not change the original string."

In [11]:

Out[11]:

"A line about Python String from the book 'Pg 191, Learning Python (O'Reilly, 5e)': Strictly speaking, Python strings are categorized as immutable sequences, meaning that the characters they contain have a left-to-right positional order and that they cannot be changed in place. In fact, strings are the first representative of the larger class of objects called sequences that we will study here. Pay special attention to the sequence operations introduced in this post, because they will work the same on other sequence types we’ll explore later, such as lists and tuples. Note: All string methods returns new values. They do not change the original string."

In [12]:

x.count('a')

Out[12]:

In [13]:

for i in string.ascii_letters: 
    print(i, x.count(i))
    break

a 39

In [14]:

print(len(x))
print(len(x.split()))
print(len(x.split(".")))

658
105
6

In [26]:

import numpy

In [17]:

import dateutil

In [31]:

dateutil.__version__

Out[31]:

'2.8.2'

In [28]:

!pip show dateutil

WARNING: Package(s) not found: dateutil

In [24]:

d = dateutil.parser.parse("5.1.2015", dayfirst=True)

In [25]:

print(d.day, d.month, d.year)

5 1 2015

In [ ]:

In [32]:

Out[32]:

"A line about Python String from the book 'Pg 191, Learning Python (O'Reilly, 5e)': Strictly speaking, Python strings are categorized as immutable sequences, meaning that the characters they contain have a left-to-right positional order and that they cannot be changed in place. In fact, strings are the first representative of the larger class of objects called sequences that we will study here. Pay special attention to the sequence operations introduced in this post, because they will work the same on other sequence types we’ll explore later, such as lists and tuples. Note: All string methods returns new values. They do not change the original string."

In [33]:

x.find('that') # Find method of string class
print(x[x.find('that') : x.find('that') + 15])

that the charac

In [34]:

x.find('in')

Out[34]:

In [35]:

pattern = 'that'
for match in re.finditer(pattern, x):
    s = match.start()
    e = match.end()
    # print('String match "%s" at slice %d:%d' % (x[s:e], s, e))
    print('String match "{}" at slice {}:{}'.format(x[s:e], s, e))

String match "that" at slice 165:169
String match "that" at slice 240:244
String match "that" at slice 372:376

In [37]:

pattern = ' in '
for match in re.finditer(pattern, x):
    s = match.start()
    e = match.end()
    # print('String match "%s" at slice %d:%d' % (x[s:e], s, e))
    print('String match "{}" at slice {}:{}'.format(x[s:e], s, e))

String match " in " at slice 267:271
String match " in " at slice 456:460

In [86]:

country_codes = {
    "+61": "Australia",
    "+91": "India",
    "+92": "Pakistan",
    "+94": "Sri Lanka",
}

In [94]:

ph_list = []
for i in range(20):
    ph = ""
    for i in range(10): ph += str(random.randrange(1, 10))
    
    ph_list.append(random.choice(list(country_codes.keys())) + ph)

In [95]:

ph_list

Out[95]:

['+916931271267',
  '+917651179969',
  '+946537287864',
  '+943685549868',
  '+916145595723',
  '+611998419265',
  '+916486522229',
  '+612254354296',
  '+942451896152',
  '+928729946665',
  '+941189538821',
  '+613157532271',
  '+927351481817',
  '+912546373287',
  '+611138287122',
  '+617663659431',
  '+922936984789',
  '+925542964793',
  '+919929189699',
  '+914187412422']

In [88]:

random.randrange(1,10)

Out[88]:

In [77]:

string.capwords(x)

Out[77]:

"A Line About Python String From The Book 'pg 191, Learning Python (o'reilly, 5e)': Strictly Speaking, Python Strings Are Categorized As Immutable Sequences, Meaning That The Characters They Contain Have A Left-to-right Positional Order And That They Cannot Be Changed In Place. In Fact, Strings Are The First Representative Of The Larger Class Of Objects Called Sequences That We Will Study Here. Pay Special Attention To The Sequence Operations Introduced In This Post, Because They Will Work The Same On Other Sequence Types We’ll Explore Later, Such As Lists And Tuples. Note: All String Methods Returns New Values. They Do Not Change The Original String."

In [ ]:

In [100]:

phn = ['+916931271267',
  '+917651179969',
  '+946537287864',
  '+943685549868',
  '+916145595723',
  '+611998419265',
  '+916486522229',
  '+612254354296',
  '+942451896152',
  '+928729946665',
  '+941189538821',
  '+613157532271',
  '+927351481817',
  '+912546373287',
  '+611138287122',
  '+617663659431',
  '+922936984789',
  '+925542964793',
  '+919929189699',
  '+914187412422']

country_codes = {
    "+61": "Australia",
    "+91": "India",
    "+92": "Pakistan",
    "+94": "Sri Lanka",
}

for i in phn:
    # Picking first three characters would be incorrect because
    # you have country codes like: +1 (for US, Canada) 
    # and +254 (for Kenya)
    
    for j in country_codes:
        if (i.startswith(j)):
            print(i, country_codes[j])

+916931271267 India
+917651179969 India
+946537287864 Sri Lanka
+943685549868 Sri Lanka
+916145595723 India
+611998419265 Australia
+916486522229 India
+612254354296 Australia
+942451896152 Sri Lanka
+928729946665 Pakistan
+941189538821 Sri Lanka
+613157532271 Australia
+927351481817 Pakistan
+912546373287 India
+611138287122 Australia
+617663659431 Australia
+922936984789 Pakistan
+925542964793 Pakistan
+919929189699 India
+914187412422 India

In [ ]:

In [102]:

print('+917651179969'.startswith('+91'))
print('+917651179969'.startswith('+92'))

True
False

In [ ]:

In [108]:

dates_of_birth = ['01/01/2003', '02/01/2004', '07/07/2003',
                  '03/02/2003', '04/03/2004', '05/03/2004']

In [110]:

for i in dates_of_birth:
    if i.endswith('2003'): print(i)

01/01/2003
07/07/2003
03/02/2003

In [ ]:

In [1]:

x = "I love programming"

In [2]:

x.split()

Out[2]:

['I', 'love', 'programming']

In [3]:

y = "Suresh,Ashish,Jim,Jack"

In [5]:

y.split(",")

Out[5]:

['Suresh', 'Ashish', 'Jim', 'Jack']

In [38]:

z = "Suresh,Ashish.Jim,Jack.Vaibhav" # Two separators "," and "."

In [39]:

re.split("[.,]", z)

Out[39]:

['Suresh', 'Ashish', 'Jim', 'Jack', 'Vaibhav']

In [44]:

z = '''Hello, there!
Am here to code.
Happy Learning!
Here was a multiline string!
'''

In [45]:

Out[45]:

'Hello, there!\nAm here to code.\nHappy Learning!\nHere was a multiline string!\n'

In [46]:

z.split("\n")

Out[46]:

['Hello, there!',
  'Am here to code.',
  'Happy Learning!',
  'Here was a multiline string!',
  '']

In [47]:

z.splitlines()

Out[47]:

['Hello, there!',
  'Am here to code.',
  'Happy Learning!',
  'Here was a multiline string!']

Form Validation¶

In [53]:

age = input("Enter your age (in years):")

In [54]:

str(age).isdigit()

Out[54]:

False

In [58]:

first_name = input("Enter your first name:")

In [59]:

first_name.isalpha()

Out[59]:

True

In [ ]:

survival8

Saturday, June 3, 2023

String Related Functionality in Python

Some Commonly Used String Methods

A more exhaustive list

Count of each alphabet

Count of characters, count of words and count of sentences in a given string

split()

Find first occurence of ‘that’, and find all occurences of the word ‘that’

Startswith() and Endswith()

Split and SplitLines

Note About String in Python

Now in code

Form Validation¶

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