Assign scientific notation to variable in Python

Question

I am trying to ask for a float variable, then assign its scientific notation to it and then use that notation in the following operations. As in, I want the program to actually work with the notation, not just return the results in it. I managed to convert variable by using the print function:

def estim(abs(x)):
    a=print("{:.3e}".format(x))
    return a

However that does not actually assign the scientific value to x. I then tried

b=float(a)

but a is None type, so it doesn't work. Any help?

Edit: by scientific notation I mean X.YYYe+Z, example: 31234.34234 -> 3.12e+04

Well, your code makes no sense. Maybe, a="{:.3e}".format(x) will work? — ForceBru
– ForceBru, Commented Jan 29, 2015 at 19:40
In Python floats don’t internally work using “decimal notation” or “scientific notation.” These are only output formats. What do you mean by “work with the notation”? — Gandaro
– Gandaro, Commented Jan 29, 2015 at 19:42
I meant that instead of understading 44432.12, the program would consider it as 4.44*10^4, for instance, so actually 44400. @ForceBru ' s suggestion seems to work, thank you. — L.R.
– L.R., Commented Jan 29, 2015 at 19:46
@L.R. 31234.34234 -> 3.12e+04 ... You need a="{:.2e}".format(x) and not a="{:.3e}".format(x). (Now don't edit) — Bhargav Rao
– Bhargav Rao, Commented Jan 29, 2015 at 19:49
What is it you want to do with this number? Scientific notation is a means of displaying a number. It doesn't change what the number is. So it only makes sense to "work with the number in scientific notation" if what you really want is to work with a string representation of it. — BrenBarn
– BrenBarn, Commented Jan 29, 2015 at 19:52

ForceBru · Accepted Answer · 2015-01-29 19:47:26Z

3

You need to use a="{:.3e}".format(x)

Here is an example

x=246789;
a="{:.3e}".format(x);
print a;
print float(a);

Output

2.468e+05
246800.0

answered Jan 29, 2015 at 19:47

ForceBru

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Comments

Bhargav Rao · Accepted Answer · 2015-01-29 20:01:45Z

1

If you do "{:.3e}".format(x) you will get 3 digits after decimal, that is

>>> a = 31234.34234
>>> "{:.3e}".format(a)
'3.123e+04'

To get what you want, you need to do "{:.2e}".format(x).

>>> "{:.2e}".format(a)
'3.12e+04'
>>> float("{:.2e}".format(a))
31200.0

Converting it back to float will give you the original value

As a function

def estim(x):
    x = abs(x)
    a=("{:.2e}".format(x))
    print(a)
    return a

Tip:

You can use % (It might be deprecated)

>>> a = 31234.34234
>>> "%e"%a
'3.123434e+04'

edited Jan 29, 2015 at 20:01

answered Jan 29, 2015 at 19:46

Bhargav Rao

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1 Comment

Gandaro Over a year ago

The code for the estim function you gave does not work: “SyntaxError: invalid syntax.”

Steve Barnes · Accepted Answer · 2015-01-29 19:47:08Z

1

The returned value from a print is always None I suspect what you need is more along the lines of:

def estim(x):
    a="{:.3e}".format(abs(x))
    print a
    return a

answered Jan 29, 2015 at 19:47

Steve Barnes

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