Namaste Coders!

In this article, we will discover the Strings in Python😍.

What are strings?

Anything written within single, double or triple quotes is a string.

So simple it is, isn't it 😎?

Python has a built-in string class named ”str” with many handy features (there is an older module named ”string” which you should not use).

# strings in python

s1='python'
s2="programming"

Why we have two ways of defining strings🤔?

This can be explained from following example👇

# If you want to use single quote as a part of string 
s="Let's begin with Python"

# If you want to add double quotes as a part of string
s2='" Coding is about debugging "'

print(s)
print(s2)

Output

Let's begin with Python

" Coding is about debugging "

Properties of Strings

• Strings are iterable which means we can loop it.
• We can get individual element from a list by indexing.
• Strings are immutable that means you cannot change the strings once declared.

Escape characters can also be used inside strings by using slash.\n (for new line), \t (space ),\’(single quote),\b(back space)

# Using Escape sequence
s='let\'s\nbegin\tprogramming'
print(s)
# To use slash as a character and not escape sequence
s2=r'C:\newfolder'
print(s2)

Output

let's

begin programming

C:\newfolder

Indexing

Each item in a list corresponds to an index number, which is an integer value, starting with the index number 0.

Strings also follow negative indexing from right to left beginning from -1.

Negative Indexing

s="kiwi"
print("index 0: ",s[0])  # index 0:  k
print("index 1: ",s[1])  # index 1:  i
print("index 2: ",s[2])  # index 2:  w
print("index 3: ",s[3])  index 3:  i

# Reverse indexing
print("index -1: ",s[-1])  # index -1:  i
print("index -2: ",s[-2])  # index -2:  w
print("index -3: ",s[-3])  # index -3:  i
print("index -4: ",s[-4])  # index -4:  k

Immutability of Strings

Strings are immutable. Thus, we cannot change value in a string.

s="Python"
s[5]='@'
print(s)

It will through TypeError

Concatenation

In Python, (+) operator is used for joining two strings,It is called concatenation.

s1="python"
s2="programming"
print(s1+' '+s2)  # python programming

String Methods

- s.lower()

returns the lowercase version of the string

s="Python PROGRAMMING"
print(s.lower())
# 'python programming'

- string_name.upper()

returns the uppercase version of the string

s="Python PROGRAMMING"
print(s.upper())
# 'PYTHON PROGRAMMING'

- string_name.strip()

returns a string with whitespace removed from the start and end.

s='    python      '
print(s.strip())
# 'python'

string_name.isalpha()

tests if all the string chars are alphabets

s="python"
print(s.isalpha())
# True

s="python3"
print(s.isalpha())
# False

string_name.isdigit()

tests if all the string chars are digits.

s="python123"
print(s.isdigit())
# False

s="123"
print(s.isdigit())
# True

string_name.isspace()

tests if all the string chars are spaces.

s="123"
print(s.isspace())
# False

s=" "
print(s.isspace())
# True

string_name.startswith(’sub_string’)

returns True if the string starts with the given other string.

s="python programming"
print(s.startswith('o'))
# False
print(s.startswith('p'))
# True

string_name.endswith(’sub_string’)

returns True if the string endswith the given other string.

s="python programming"
print(s.endswith('o'))
# False
print(s.endswith('g'))
# True

string_name.find(sub_string)

searches for the given other string (not a regular expression) within s, and returns the first index where it begins or -1 if not found

s='python'
print(s.find('y'))
# 1
print(s.find('a'))
# -1

string_name.replace('old' , 'new')

returns a string where all occurrences of 'old string' have been replaced by 'new string'.

s="python"
print(s.replace('o','@'))
# 'pyth@n'

string_name.split('delim')

returns a list of substrings separated by the given delimiter. The delimiter is not a regular expression, it’s just text. ’aaa,bbb,ccc’.split(’,’) -> [’aaa’, ’bbb’, ’ccc’]. As a convenient special case s.split() (with no arguments) splits all the values.

s="python programming is best"
print(s.split(" "))
# ['python', 'programming', 'is', 'best']

print(s.split(" ")[1])
# 'programming'

print(s.split( "p"))
#['', 'ython ', 'rogramming is best']

string_name.join(list)

opposite of split(), joins the elements in the given list together using the string as the delimiter. e.g. ’—’.join([’ram’, ’sham’, ’sam’]) -> ram—sham—sam

s=["ram","sham","sam"]
 print((',').join(s))
# 'ram,sham,sam'

print(('-').join(s))
# 'ram-sham-sam'

Slicing

Slicing is a very fun loving technique of lists. It allows us to fetch a part from string. One can use both negative and positive indexing in it.end_index is exclusive whereas start_index is inclusive.

syntax

string_name[start_index:end_index:space]

Example

s="python programming"
print(s[: :])  # python programming
print(s[:2])  # py
print(s[-5:-2])  # mmi
print(s[: : -1])  # gnimmargorp nohtyp

Repeating string

we can repeat a string as many time just by using * operator

s="python"*5
print(s)
# 'pythonpythonpythonpythonpython'

Various Print Formats

There are various print formats which makes printing strings very easy rather than using (+) operator again and again.

# classic approach
print(str(n1) + " + "+ str(n2) +" = "+str(ans))  #43 + 53 = 96

# using .format
# In it we have to provide placeholders where we can fill the values
print('{} + {} = {}'.format(n1,n2,ans))  #43 + 53 = 96

# using access specifier
# %d for integer %f for decimal point %s for string
print('%d + %d = %d'%(n1,n2,ans))  #43 + 53 = 96

# f-strings
# It is best approach as we specify variable names within print statement
# It avoids confusion as we do not need to maintain any tuple
print(f'{n1} + {n2} = {ans}')  #43 + 53 = 96

The End

I hope you enjoyed the article and had a good learning experience.

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