That's a dict comprehension.

It is just like a list comprehension

 [3*x for x in range(5)]
 --> [0,3,6,9,12]

except:

{x:(3*x) for x in range(5)}
---> { 0:0, 1:3, 2:6, 3:9, 4:12 }

• produces a Python dictionary, not a list
• uses curly braces {} not square braces []
• defines key:value pairs based on the iteration through a list

In your case the keys are coming from the Code property of each element and the value is always set to empty array []

The code you posted:

order.messages = {c.Code:[] for c in child_orders}

is equivalent to this code:

order.messages = {}
for c in child_orders:
    order.messages[c.Code] = []

See also:

• PEP0274
• Python Dictionary Comprehension

Here is where you'll find the documentation for this method of formatting.

The "brackets" in your example constructs a new list from an old one, this is called list comprehension.

The basic idea with [f(x) for x in xs if condition] is:

def list_comprehension(xs):
    result = []
    for x in xs:
        if condition:
            result.append(f(x))
    return result

The f(x) can be any expression, containing x or not.

Curly braces are also used for sets. This is a set comprehension. It creates the set of 20 requests.get objects, keeping only the unique ones.

If you use [] instead of {} it is a list comprehension. They are similar, but have two differences

• the list is ordered
• the list can have duplicate elements

Also, as you mention, this is a bad way to make requests. Comprehensions should be used for creating a list/set, not for calling a number of commands as a by-product. In that case, a simple for-loop is better, it makes the intent clearer.

You have to use indentation to represent something is for something else: python for x in range(10): # all code indented are in the for loop print("This is *in* the for loop!") print("So as this!") print("This is OUTSIDE of the for loop because it isn't indented.") This is just a simple example, but it can get more complicated: ```python for x in range(10): # This is in the loop print("We are currently on the number {}!".format(x)) if x == 5: # This is in the if statenent which is in the loop print("Cool! 5!") if x % 2 == 0: # This is in a different if statement but still in the loop print("Alright! {} is an even number!".format(x)) # This is in the for loop but not in a if statement print("Next number coming up... {}!".format(x+1)) This code isn't in any kind of block print("Finished!") ``` This is why Python is so picky about indentation. If you forgot to indent like this: python for x in range(5): if x == 5: break Python will cause an Syntax Error because it thought you put nothing in the if statement and there has to be something. Python also will think that the break command is part of the loop, but we really don't mean that. Keep in mind that you have to be very careful indenting when you are a beginner! You get used to it when you get more advanced :) I hope this helps. ~Alex

You can try to add support for braces using a future import statement, but it's not yet supported, so you'll get a syntax error:

>>> from __future__ import braces
  File "<stdin>", line 1
SyntaxError: not a chance

No, there's no alternative to correct indentation. It's a fundamental part of the language.

I have so much problem with indentations...

Perhaps you could benefit from a better editor. A good code editor or IDE will auto-indent code for you. Avoid using something like Notepad which always starts new lines at column 1. The bare minimum you need is an editor that will start new lines at the same indentation level as the previous line.

...as for long codes it makes the code less readable.

I don't see how that can be true. Bad indentation is one of the most pervasive problems I see with new coders' code. It makes code super hard to read. It's like having poor punctuation or capitalization in English. Indentation is a basic readability tool.

Can we use curly brackets?

It scares me a little that you want to forego good indentation and use curly braces instead. Even if curly braces were allowed, you should still indent your code properly. Don't you find this

if (foo) {
    while (bar != baz) {
        quux();
    }
}

easier to read than this?

  if (foo) {
while (bar != baz) {
    quux();         }
    }

And if you already indent your code as a matter of habit the curly braces are redundant. That's what led Python's designers to remove them.

if foo:
    while bar != baz:
        quux()