If a dictionary key has a Python list as its value!

[Varuna Seneviratna]

If a dictionary key has a Python list as its value, you can read the values
one by one in the list using a for-loop like in the following.

d = {k: [1,2,3]}

print(v)

No tutorial describes this, why?
What is the Python explanation for this behaviour?

Varuna

[MRAB]

Post by Varuna Seneviratna
If a dictionary key has a Python list as its value, you can read the values
one by one in the list using a for-loop like in the following.
d = {k: [1,2,3]}

print(v)

No tutorial describes this, why?
What is the Python explanation for this behaviour?

If the value is a list, you can do list things to it.

If the value is a number, you can do number things to it.

If the value is a string, you can do string things to it.

And so on.

It's not mentioned in tutorials because it's not special. It just
behaves how you'd expect it to behave.

[Mats Wichmann]

Post by Varuna Seneviratna
If a dictionary key has a Python list as its value, you can read the values
one by one in the list using a for-loop like in the following.
d = {k: [1,2,3]}

print(v)

No tutorial describes this, why?
What is the Python explanation for this behaviour?

Sorry... why is this a surprise? If an object is iterable, you can
iterate over it.

Post by Varuna Seneviratna

d = {'key': [1, 2, 3]}
type(d['key'])

<class 'list'>

Post by Varuna Seneviratna

val = d['key']
type(val)

<class 'list'>
... print(v)
...
...
1
2
3

[Stefan Ram]

Post by Varuna Seneviratna
If a dictionary key has a Python list as its value, you can read the values
one by one in the list using a for-loop like in the following.
d = {k: [1,2,3]}

print(v)

No tutorial describes this, why?
What is the Python explanation for this behaviour?

This is explained by extensionality: To find the behavior of
"for v in ...", the only thing one needs to know about "..."
is its value. You could just as well have written:

l = d[ k ]
for v in l:

. l can be any iterable. It does not matter where it came from.
It does not matter that it cam from a dictionary. There are thousand
places where it could have come from, and no tutorial can name them
all.