How to convert floats into double to stuct pack?

Asked Jan 27 '20 at 18:47

Active Jan 27 '20 at 18:47

Viewed 62 times

I'm trying to pack a struct that looks like this on c++:

typedef struct {
    double    var1
    double    var2
} myType;

In my python script I have the user enter 2 inputs that I cast to a float.

var1 = float(input())
var2 = float(input())
payload = struct.pack("dd", var1, var2)

Now this won't work because I'm trying to send floats in as doubles. Is there anyway to get this working? I cannot change myType so that option is off the table.

asked Jan 27 '20 at 18:47

topfoxrider

Can you not cast to `double` instead of `float`? – NathanOliver Jan 27 '20 at 18:52
Not in python no. Doubles don't exist there. – topfoxrider Jan 27 '20 at 18:55
Sidenote: You don't need `typedef` there. Just do `struct myType { double var1; double var2; };` and it'll be `typedef`:ed automatically. – Ted Lyngmo Jan 27 '20 at 18:56
Btw, when you say "_send_", do you mean that you want to serialize the struct and send it over the network or to a file or similar? – Ted Lyngmo Jan 27 '20 at 18:58
2

You're already doing it. [Python `float` *is* `double`](https://stackoverflow.com/a/6663292/10077). – Fred Larson Jan 27 '20 at 19:01
Fred, I just realized now that this was a dumb question. Apparently you're right and packing with "ff" will do the trick. – topfoxrider Jan 27 '20 at 19:03
1

No, I think you still want `"dd"`. See https://docs.python.org/3/library/struct.html#format-characters – Fred Larson Jan 27 '20 at 19:05
Jeez seems like Im the big dumb dumb. I swear using the "dd" was giving me an error but now it works :/ – topfoxrider Jan 27 '20 at 19:10
1

@topfoxrider: Don't be too hard on yourself. We've all been there. – Fred Larson Jan 27 '20 at 19:12

How to convert floats into double to stuct pack?

0 Answers0