Python use of a:[1,3]?

Question

What does this line mean in python 3.x?

a:[1,3]

Source : https://www.youtube.com/watch?v=yX8KuPZCAMo

Time: 17:40

Dupe: https://stackoverflow.com/questions/509211/understanding-pythons-slice-notation — EdChum, Jan 25 '18 at 16:58
Is it a dictionary or a List? coz dictionary is created like this a={"a_key":2,"akey1":4}?? — shiteme, Jan 25 '18 at 17:15
duh... you need to view at 17:47 the code... and Aladdin can do the rest! — ZF007, Jan 25 '18 at 17:15
@ZF007 Well spotted. It is a dictionary in the video. shiteme, dictionaries can look like `dict_of_lists = {a: [b, 7], 3: [b, c]}`, if a, b, c were defined before creating the dictionary. — Mr. T, Jan 25 '18 at 17:44

score 3 · Accepted Answer · answered Jan 25 '18 at 17:10

3

This is the syntax of a dictionary in Python, a data structure which maps an index to another object.

a = tf.placeholder(tf.float32)
{a: [1,3]}

In this case, a is a Tensor from Tensorflow and [1,3] are the values it will assume when the graph is executed.

IMO, you should invest your time into acquiring a better understanding of elementary data structures and syntax from Python before diving into Tensorflow.

answered Jan 25 '18 at 17:10

Matheus Portela

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Is it a dictionary or a List? coz dictionary is created like this a={"a_key":2,"akey1":4}?? – shiteme Jan 25 '18 at 17:16
It is a dictionary whose index is pointing to a list. – Matheus Portela Jan 25 '18 at 17:17

score 0 · Answer 2 · answered Jan 25 '18 at 17:08

0

In the video, a and b are tensorflow.python.framework.ops.Tensor Objects. At time 17:40, the instructor uses a and b as keys and their respective values [1,3] and [2, 4]. At 17:45, in the pop_up, you can see the variable name, feed_dict. He is just creating a dictionary.

answered Jan 25 '18 at 17:08

Kris

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Is it a dictionary or a List? coz dictionary is created like this a={"a_key":2,"akey1":4} – shiteme Jan 25 '18 at 17:14

score 0 · Answer 3 · answered Jan 25 '18 at 17:09

0

You didn't give us the whole context of the code.

{a:[1,3]}

defines a dictionary with key a and value [1,3].

answered Jan 25 '18 at 17:09

John Gordon

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Is it a dictionary or a List? coz dictionary is created like this a={"a_key":2,"akey1":4} – shiteme Jan 25 '18 at 17:14
Dict keys don't have to be strings; they can be any immutable value. In this case, the key is a variable `a` which was previously defined. And the value can be anything, in this case it's a list. – John Gordon Jan 25 '18 at 17:19

ZF007 · Answer 4 · 2018-02-02T21:36:44.373

-1

OP takes a part of a Dictionary out of context which can be seen at timepoint 17:47min.

a is declared as a = tf... etc and thus has content and context.

[1,3] are list items.

then a:[1,3] in dict:

a = keyname. [1,3] = values

try this:

a = 'alot of words for a keyname'
b = 17.47

my_dict = {a:["sing along song", "the voice of"], b:(12, 'candidates', None, "wins")}

print my_dict.keys()

edited Feb 02 '18 at 21:36

answered Jan 25 '18 at 17:13

ZF007

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Is it a dictionary or a List? coz dictionary is created like this a={"a_key":2,"akey1":4} – shiteme Jan 25 '18 at 17:17
its dict with declared values. `a` is here a variable name that is brought in as you can see at 17:47 in the video. – ZF007 Jan 25 '18 at 17:18

Python use of a:[1,3]?

4 Answers4