[Python] #6 Python String Objects

This is a self note while taking the online course from: LinkedIn Learning: Learning Python by Joe Marini LinkedIn Learning: Python Essential Training by Bill Weinman

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1. String

• strings are object in python and immutable.
• ___str___: built-in function for each class that is used for string representation
• common functions for string object: +(concatenate), upper(), lower(), replace(), index(), …

# subclass of string object
class MyString(str):
    def __str__(self):
        return self[::-1]

s = 'hello'
print(f'{s} -> {MyString(s)}')

(Result)

hello -> olleh

2. String Formatting

• format(a0, a1, …) function can be used with order of indices
• {str:[< or > with numbers]}: line up with the given number of whitespaces
• {number:,}: add comma(,) on the given number
• {float:.(num)f}: print the given number of floating points -{:o / b}: hexadecimal/binary

x = 42
y = 73

# string interpolation
print('the number is {} {}'.format(x, y))
print('numbers: {xx} {bb}'.format(xx=x, bb=y))
print('numbers: {0} {1} {0}'.format(x, y))

# order formatting ':' '+' ',' '._f'
print('numbers: {0:<5}. {1:>5}'.format(x, y))
print('numbers: {0:<5}. {1:>+05}'.format(x, y))
print('{:,}'.format(x*y*1298).replace(',', '.'))
print('number is {:.3f}'.format(x*y))
print('hexadecimal: {:o}\tbinary:{:b}'.format(x, x))

# F string formatting
print(f'the number is {x:.3f}')

(Result)

the number is 42 73
numbers: 42 73
numbers: 42 73 42
numbers: 42   .    73
numbers: 42   . 00+73
3.979.668
number is 3066.000
hexadecimal: 52	binary:101010
the number is 42.000

3. Split & Join

• split(): split words with spaces and new lines
• join(): concats list or tuples of strings with the given arg

# split
s = 'this is a long string with a bunch of words in it.'
l = s.split()
print(l)
print(s.split('i'))

# join
s2 = ':'.join(l)
print(s2)

(Result)

['this', 'is', 'a', 'long', 'string', 'with', 'a', 'bunch', 'of', 'words', 'in', 'it.']
['th', 's ', 's a long str', 'ng w', 'th a bunch of words ', 'n ', 't.']
this:is:a:long:string:with:a:bunch:of:words:in:it.