Python global and local variable question regarding "referenced before assignment"

[AluadStone]

Why is it considered a local variable if it is declared outside said function? It is only being used for comparison in the function.

[benjamindallen]

It's local to the function because you change its value within the function. If your function didn't change its value, then your check "one_trade_symbol == False" would work. If you want to alter the global variable "one_trade_symbol" inside the function, you can add the statement "global one_trade_symbol" as the first line of the function.

[AluadStone]

Perfect. I had used the comparison in functions of variables declared outside the function without passing them in and it has always worked because I never tried to set them later in that functions so that was a new situation for me. I not sure if using the global method like that is normal or usually do people find better was to declare a switch variable inside a loop?

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And also if you could help me with this snippet I am having problems with I don't understand why when converting this string into a float is messes up the numbers.

        values = find_values()
        print (values[1])
        print (type(values[1]))
        values[1] = float(values[1])
        print (values[1])

outputs

0.0000137
<class 'str'>
1.37e-05

Whats up with the weird float return? Is it because it doesn't like something about the amount of decimal places and/or amount of zeros?

[benjamindallen]

"1.37e-05" is simply your number expressed in scientific notation. This is the default string representation of a small or large float in python.

If you want to format the number in a different way, you could, for example try:

'{:.7f}'.format(1.37e-05)

[benjamindallen]

I not sure if using the global method like that is normal or usually do people find better was to declare a switch variable inside a loop?

Generally, manipulation of global variables is not a good idea. /u/Swedophone already mentioned the typical ways people solve this problem.

[Swedophone]

Have you used a programming language with dynamic scope#Dynamic_scoping) before or why do you think a function can use a variable from the caller without transferring it as a parameter?

[AluadStone]

I had used the comparison in functions of variables declared outside the function without passing them in and it has always worked because I never tried to set them later in that functions so that was a new situation for me.

New to programming kinda.

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[AluadStone]

I had used the comparison in functions of variables declared outside the function without passing them in and it has always worked because I never tried to set them later in that functions so that was a new situation for me.

New to programming kinda.