Important Topics :

1. Variables : Python uses 'Dynamic Typing' , Means you can reassign the variables to different data type.
EX. my_dog = 2 // Integer data typed
my_dog = ["Tom" , "John"] // list data typed

2. Strings :

>>> S = 'Spam' # Make a 4-character string, and assign it to a name
>>> len(S) # Length
4
>>> S[0] # The first item in S, indexing by zero-based position
'S'
>>> S[1] # The second item from the left
'p'

>>> S[-1] # The last item from the end in S
'm'
>>> S[-2] # The second-to-last item from the end
'a'

>>> S[-1] # The last item in S
'm'
>>> S[len(S)-1] # Negative indexing, the hard way
'm'

>>> S # A 4-character string
'Spam'
>>> S[1:3] # Slice of S from offsets 1 through 2 (not 3) //Gives us all the characters in string S from offsets 1 through 2 (that is, 1 through 3 – 1) as a new string.
'pa'

>>> S[1:] # Everything past the first (1:len(S))
'pam'
>>> S # S itself hasn't changed
'Spam'
>>> S[0:3] # Everything but the last
'Spa'
>>> S[:3] # Same as S[0:3]
'Spa'
>>> S[:-1] # Everything but the last again, but simpler (0:-1)
'Spa'
>>> S[:] # All of S as a top-level copy (0:len(S))
'Spam'

>>> S + 'xyz' # Concatenation
'Spamxyz'
>>> S # S is unchanged
'Spam'
>>> S * 8 # Repetition
'SpamSpamSpamSpamSpamSpamSpamSpam'

>>> S
'Spam'
>>> S[0] = 'z' # Immutable objects cannot be changed
...error text omitted...
TypeError: 'str' object does not support item assignment
>>> S = 'z' + S[1:] # But we can run expressions to make new objects
>>> S
'zpam'

>>> S = 'shrubbery'
>>> L = list(S) # Expand to a list: [...]
>>> L
['s', 'h', 'r', 'u', 'b', 'b', 'e', 'r', 'y']
>>> L[1] = 'c' # Change it in place
>>> ''.join(L) # Join with empty delimiter
'scrubbery'
>>> B = bytearray(b'spam') # A bytes/list hybrid (ahead)
>>> B.extend(b'eggs') # 'b' needed in 3.X, not 2.X
>>> B # B[i] = ord(c) works here too
bytearray(b'spameggs')
>>> B.decode() # Translate to normal string
'spameggs'

>>> S = 'Spam'
>>> S.find('pa') # Find the offset of a substring in S
1
>>> S
'Spam'
>>> S.replace('pa', 'XYZ') # Replace occurrences of a string in S with another
'SXYZm'
>>> S
'Spam'

>>> line = 'aaa,bbb,ccccc,dd'
>>> line.split(',') # Split on a delimiter into a list of substrings
['aaa', 'bbb', 'ccccc', 'dd']
>>> S = 'spam'
>>> S.upper() # Upper- and lowercase conversions
'SPAM'
>>> S.isalpha() # Content tests: isalpha, isdigit, etc.
True

>>> S = 'A\nB\tC' # \n is end-of-line, \t is tab
>>> len(S) # Each stands for just one character
5
>>> ord('\n') # \n is a byte with the binary value 10 in ASCII
10
>>> S = 'A\0B\0C' # \0, a binary zero byte, does not terminate string
>>> len(S)
5

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