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>>> # list comprehension
>>> l = []
>>> # create a list l that contains only even int from 0 to 10
>>> [0, 2, 4, 6, 8, 10]
[0, 2, 4, 6, 8, 10]
>>> # Method #1 W/o comprehension
>>> for i in range(0, 11, 2):
l.append(i)
>>> l
[0, 2, 4, 6, 8, 10]
>>> # Method #2 W/ comprehension
>>> list_2 = [i for i in range(0, 11, 2)]
>>> list_2
[0, 2, 4, 6, 8, 10]
>>> # Method #1
>>> # iterate a for loop with range as req start = 0, stop =11, step =2
>>> # value ret by range is APPENDED to an empty list
>>> # Method # 2
>>> ## list_2a = [ <loop variable> || <for loop>]
>>> # <for loop> -> for i in range(0, 11, 2) ## Colons are omitted
>>> # <loop variable> -> i
>>> list_2a = [i for i in range(0, 11, 2)]
>>> list_2a
[0, 2, 4, 6, 8, 10]
>>> l = []
>>> for i in range(0, 11, 2):
l.append(i)
>>> # Goal of list comprehension to create a NEW LIST
>>> [ s for s in range(1, 10)]
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> p = []
>>> for s in range(1, 10):
p.append(s)
>>> p
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> "123456789"
'123456789'
>>> # create a list of digits and each ele in list should be of type int
>>> q = []
>>> s = "123456789"
>>> s
'123456789'
>>> list(s)
['1', '2', '3', '4', '5', '6', '7', '8', '9']
>>> q
[]
>>> for i in s:
i_int = int(i) # convert each char in str to int
q.append(i_int) # append the converted integer to the list
>>> q
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> # Verify whether each element of list q is int
>>> for j in q:
print(type(j))
<class 'int'>
<class 'int'>
<class 'int'>
<class 'int'>
<class 'int'>
<class 'int'>
<class 'int'>
<class 'int'>
<class 'int'>
>>> for j in q:
print(isinstance(j, int))
True
True
True
True
True
True
True
True
True
>>> q.append('21') # a value of type str is appended to demonstrate
usage of isinstance function
>>> q
[1, 2, 3, 4, 5, 6, 7, 8, 9, '21']
>>> for j in q:
print(isinstance(j, int))
True
True
True
True
True
True
True
True
True
False
>>> # because the last ele of q is of type str the isinstance returned False at the end
>>> q.pop() # revert q to it's original value
'21'
>>> q
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> q_comprehension = [int(i) for i in s]
>>> q_comprehension
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> q
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> q_comprehension_check_type = [isinstance(i,int) for i in
q_comprehension] # q_comprehension_check_type is list of the booleans such that
>>> # q_comprehension_check_type states whether q_comprehension[i] is an int type.
>>> # <i> is any index
>>> q_comprehension_check_type
[True, True, True, True, True, True, True, True, True]
>>> q_comprehension_check_type = [(isinstance(i,int), i) for i in
q_comprehension]
>>> # each ele of q_comprehension_check_type is a tuple with a pair of values
# the first element of tuple indicates whether the value is an int, the second ele the value itself
>>> q_comprehension_check_type
[(True, 1), (True, 2), (True, 3), (True, 4), (True, 5), (True, 6), (True, 7), (True, 8), (True, 9)]
>>> convert
>>> # w/o comprehension
>>> s
'123456789'
>>> w = []
>>> w_t_c = []
>>> counter = 0
>>> for i in s:
w.append(int(i))
w_t_c.append(isinstance(w[counter], int))
counter = counter + 1
>>> w
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> w_t_c
[True, True, True, True, True, True, True, True, True]
>>> w = []
>>> w_t_c = []
>>> counter = 0
>>> for i in s:
w.append(int(i))
w_t_c.append((isinstance(w[counter], int), w[counter]))
counter = counter + 1
>>> w
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> w_t_c
[(True, 1), (True, 2), (True, 3), (True, 4), (True, 5), (True, 6),
(True, 7), (True, 8), (True, 9)]
