str to float (rounded)

[Nader]

Hello,

I have a list of tuple with strin elements. These elements are number,
but they are save as string. Now I will change the string to number
which will be rounded. An example will make it more clear.

t = [('35.757', '-0.239'), ('33.332', '-2.707'), ('33.640', '-2.423')]

And I will have the next list:

t = [(35.76, -2.24), (33.33, -2.71), (33.64, -2.42)]

The elements of tuple are not more as string.

Would somebody tell me how I can do that?

Regards,
Nader

[Diez B. Roggisch]

Re: str to float (rounded)

Nader wrote:

Hello,
>
I have a list of tuple with strin elements. These elements are number,
but they are save as string. Now I will change the string to number
which will be rounded. An example will make it more clear.
>
t = [('35.757', '-0.239'), ('33.332', '-2.707'), ('33.640', '-2.423')]
>
And I will have the next list:
>
t = [(35.76, -2.24), (33.33, -2.71), (33.64, -2.42)]
>
The elements of tuple are not more as string.
>
Would somebody tell me how I can do that?

use

float("123.45")

to convert a string to a float.

Of course you need to do that on all your elements above by e.g. a
list-comprehension.

Diez

[Nader]

Re: str to float (rounded)

On Jun 10, 4:30 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Nader wrote:

Hello,

>

I have a list of tuple with strin elements. These elements are number,
but they are save as string. Now I will change the string to number
which will be rounded. An example will make it more clear.

>

t = [('35.757', '-0.239'), ('33.332', '-2.707'), ('33.640', '-2.423')]

>

And I will have the next list:

>

t = [(35.76, -2.24), (33.33, -2.71), (33.64, -2.42)]

>

The elements of tuple are not more as string.

>

Would somebody tell me how I can do that?

>
use
>
float("123.45")
>
to convert a string to a float.
>
Of course you need to do that on all your elements above by e.g. a
list-comprehension.
>
Diez

If I do the next :

t1 = [(round(float(x) ,1), round(float(y), 2)) for x, y in t]

I get the long float as :

[(35.79999999999 9997, -0.2399999999999 9999), (33.29999999999 9997,
-2.71), (33.60000000000 0001,-2.4199999999999 999)]

But I would have a float with 2 decimal numbers.

[Diez B. Roggisch]

Re: str to float (rounded)

>

If I do the next :
>
t1 = [(round(float(x) ,1), round(float(y), 2)) for x, y in t]
>
I get the long float as :
>
[(35.79999999999 9997, -0.2399999999999 9999), (33.29999999999 9997,
-2.71), (33.60000000000 0001,-2.4199999999999 999)]
>
But I would have a float with 2 decimal numbers.

There is no such thing as a float with only two decimal numbers. This has
been discussed on this ML a bazillion times - what you see above are
rounding errors due to the approximation of decimal values by binary
floating points.

You can *convert a float to a string* and specify a precision when printing:

>>print "%.2f" % 2.4199999999999 999999999999

2.42

Or you can use the module decimal to work with numbers base 10 - which you
can also limit to certain precisions. See a recent thread on this ML,
google for "Alternativ e to decimal type"


Diez