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How are you supposed to break up a very long list comprehension?
[something_that_is_pretty_long for something_that_is_pretty_long in somethings_that_are_pretty_long] I have also seen somewhere that people that dislike using '\' to break up lines, but never understood why. What is the reason behind this?
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So what's the difference between Generator Expressions and List Comprehensions? The generator yields one item at a time and generates item only when in demand. Whereas, in a list comprehension, Python reserves memory for the whole list. Thus we can say that the generator expressions are memory efficient than the lists.
The concept of a break or a continue doesn't really make sense in the context of a map or a filter , so you cannot include them in a comprehension.
List comprehensions and generators are not different at all; they are just different ways of writing the same thing. A list comprehension produces a list as output, a generator produces a generator object.
The only difference between Generator Comprehension and List Comprehension is that the former uses parentheses.
[x for x in (1,2,3) ] works fine, so you can pretty much do as you please. I'd personally prefer
[something_that_is_pretty_long for something_that_is_pretty_long in somethings_that_are_pretty_long] The reason why \ isn't appreciated very much is that it appears at the end of a line, where it either doesn't stand out or needs extra padding, which has to be fixed when line lengths change:
x = very_long_term \ + even_longer_term_than_the_previous \ + a_third_term In such cases, use parens:
x = (very_long_term + even_longer_term_than_the_previous + a_third_term) You can also make use of multiple indentations in cases where you're dealing with a list of several data structures.
new_list = [ { 'attribute 1': a_very_long_item.attribute1, 'attribute 2': a_very_long_item.attribute2, 'list_attribute': [ { 'dict_key_1': attribute_item.attribute2, 'dict_key_2': attribute_item.attribute2 } for attribute_item in a_very_long_item.list_of_items ] } for a_very_long_item in a_very_long_list if a_very_long_item not in [some_other_long_item for some_other_long_item in some_other_long_list ] ] Notice how it also filters onto another list using an if statement. Dropping the if statement to its own line is useful as well.
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