Sunday, September 16, 2018

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Python Ninja bootcamp 5-Strings

by SN Gurukul on September 16, 2018 in Basic Python

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In this Python lecture, we will learn about the Strings.

"String is set of sequence of characters represented in quotation marks".

"String is ordered a collection of immutable elements".

String is either define under single quote or double quote.

Let's look at String example-

Create Strings

# Single word

'hello'

>> 'hello'

# Entire Sentence

'Welcome to Python Ninja Bootcamp'

>> ' Welcome to Python Ninja Bootcamp '

We can also use double quotes

" Welcome to Python Ninja Bootcamp "

>> ' Welcome to Python Ninja Bootcamp '

#Be careful with quotes
'I'm Mayank'

>> SyntaxError: invalid syntax

We are getting syntax error because single quotes is close after is 'I'. Instead of that we can use combination of single quotes and double quotes

" I'm Mayank "

>> " I'm Mayank "

We can also put a double quote inside a single quote

'" Life is beautiful "'

>> '" Life is beautiful "'

Print a string

'Hello World1'

'Hello World2'

>> 'Hello World2'

We can use print function to print both the strings

print('Hello World1')

print('Hello World2')

>> Hello World1
>> Hello World2

# \n Breaks the line

print('This is the first.\n And this Second line.')

>> This is the first.
And this is Second line.

# \t Creates the spaces

print('This is the first.\t And this Second line.')

>> This is the first . And this is Second line.

# len() Calculates the length of string

len('hello world')

>> 11

Now assign a String to a variable

x = 'hello world'

print(x)

>> hello world

String Indexing

We have x is equal to 'hello world'

x[0] # garbs the letter at index 0

>> h

x[2] # garbs the letter at index 2

>> l

x[-1] # garbs the last letter

>> d

String Slicing

We can use : (colon) to perform slicing

x[1:] # garbs everything from the first index

>> ello world

x[:] # garbs everything

>> hello world

x[:3] # garbs everything from first index 0 to third index(excluded)

>> hel

x[:-1] # garbs everything from 0 index to the last index(excluded)

>> hello worl

x[1:5:2] # garbs every 2nd element from the 1st index to 5th index(excluded)

>> el

*Important Syntax

x[::-1] #  Reverse the string

>> dlrow olleh

x[1:5:2] # garbs every 2nd element from the 1st index to 5th index(excluded)

>> el

String Properties

Immutability

Once String is created, the elements within it cannot be changed or replaced.

We have x is equal to hello world

x[0]='a'

>> TypeError: 'str' object does not support item assignment

We can concatenate the string.

x + ' concatenate '

>> hello world concatenate

Built-in Function

We have x is equal to hello world

x.upper() # Convert the string to uppercase

>> HELLO WORLD

Note: If press TAB after x. in Juypter notebook. It will show the list of functions available in the string.

x.lower() # Convert the string to lowercase

>> hello world

x.split() # Split the string at Space by default

>>[' hello',' world' ]

x.split('o') # Split the string at 'o'

>> [ ' hell ',' w ', ' rld ' ]

Practice other built-in functions.

EDITS ARE WELCOMED!!

In the next Blog, we will discuss Print formatting

https://sngurukuls247.blogspot.com/2018/09/python-ninja-bootcamp-6-print-formatting.html

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