What is the proper way to format a multi-line dict in Python?
Since your keys are strings and since we are talking about readability, I prefer :
mydict = dict(
key1 = 1,
key2 = 2,
key3 = 3
)
First of all, like Steven Rumbalski said, "PEP8 doesn't address this question", so it is a matter of personal preference.
I would use a similar but not identical format as your format 3. Here is mine, and why.
my_dictionary = { # Don't think dict(...) notation has more readability
"key1": 1, # Indent by one press of TAB (i.e. 4 spaces)
"key2": 2, # Same indentation scale as above
"key3": 3, # Keep this final comma, so that future addition won't show up as 2-lines change in code diff
} # My favorite: SAME indentation AS ABOVE, to emphasize this bracket is still part of the above code block!
the_next_line_of_code() # Otherwise the previous line would look like the begin of this part of code
bad_example = {
"foo": "bar", # Don't do this. Unnecessary indentation wastes screen space
"hello": "world" # Don't do this. Omitting the comma is not good.
} # You see? This line visually "joins" the next line when in a glance
the_next_line_of_code()
btw_this_is_a_function_with_long_name_or_with_lots_of_parameters(
foo='hello world', # So I put one parameter per line
bar=123, # And yeah, this extra comma here is harmless too;
# I bet not many people knew/tried this.
# Oh did I just show you how to write
# multiple-line inline comment here?
# Basically, same indentation forms a natural paragraph.
) # Indentation here. Same idea as the long dict case.
the_next_line_of_code()
# By the way, now you see how I prefer inline comment to document the very line.
# I think this inline style is more compact.
# Otherwise you will need extra blank line to split the comment and its code from others.
some_normal_code()
# hi this function is blah blah
some_code_need_extra_explanation()
some_normal_code()
I use #3. Same for long lists, tuples, etc. It doesn't require adding any extra spaces beyond the indentations. As always, be consistent.
mydict = {
"key1": 1,
"key2": 2,
"key3": 3,
}
mylist = [
(1, 'hello'),
(2, 'world'),
]
nested = {
a: [
(1, 'a'),
(2, 'b'),
],
b: [
(3, 'c'),
(4, 'd'),
],
}
Similarly, here's my preferred way of including large strings without introducing any whitespace (like you'd get if you used triple-quoted multi-line strings):
data = (
"iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABG"
"l0RVh0U29mdHdhcmUAQWRvYmUgSW1hZ2VSZWFkeXHJZTwAAAEN"
"xBRpFYmctaKCfwrBSCrRLuL3iEW6+EEUG8XvIVjYWNgJdhFjIX"
"rz6pKtPB5e5rmq7tmxk+hqO34e1or0yXTGrj9sXGs1Ib73efh1"
"AAAABJRU5ErkJggg=="
)