In [ ]:

    

# list comprehensions are expressions notated with [] that build lists using iteration


    

In [2]:

    

# if you just want to make a list from an iterable, use list()

a = list('fish')
a[1] = 'o'
a


    

    
Out[2]:





['f', 'o', 's', 'h']

In [5]:

    

# if you want to do some operation on the iteration variable, use list comprehensions

[x + '!' for x in 'fish']


    

    
Out[5]:





['f!', 'i!', 's!', 'h!']

In [7]:

    

# list comprehensions support if for conditional inclusion in result
[4 for x in 'fish' if x != 'i']


    

    
Out[7]:





[4, 4, 4]

In [10]:

    

# you can also use for/in and append to construct cases that would not be possible
# with list comprehensions
result = []

for x in 'fish':
    if x != 'i':
        result.append(x)
    result.append('foo')

result


    

    
Out[10]:





['f', 'foo', 'foo', 's', 'foo', 'h', 'foo']

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# if your list comprehension is too long, consider for/append instead