Assign a function to multiple variables

Question

Can someone please explain to me in the code below. Why if we assign multiple variables (beans, jars, crates) to a single function(secret_formula(start_point)), each variable later has different value. I thought that if we assign in this way all variables will have the same value.So why this happens?

def secret_formula(started):
    jelly_beans = started * 500
    jars = jelly_beans / 1000
    crates = jars / 100
    return jelly_beans, jars, crates

start_point = 10000

# ?
beans, jars, crates = secret_formula(start_point)

print(f"We'd have {beans} beans, {jars} jars, and {crates} crates.")

Asked By: Escape

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Answer 1

Your function secret_formula returns 3 values, jelly_beans, jars, and crates. You have the option of storing that all as one variable or unpacking it into three variables.

For example, one variable, but you access the values because the variable is a list:

all_values = secret_formula(start_point)

beans = all_values[0]
jars = all_values[1]
crates = all_values[2]

This is done faster and equivalently just by unpacking it with three variables, which is what your code example does.

beans, jars, crates = secret_formula(start_point)

Answered By: Michael Cao

Answer 2

When in your function you return jelly_beans, jars, crates, this creates a tuple containing those three independent values.

When calling that function and assigning it to beans, jars, crates, you unpack each value from the returned tuple into three independent variables

Answered By: ljmc

Answer 3

This has to be a dupe, but I couldn’t find it in a cursory search..

If you assign to multiple variables, Python does not repeat the value. It instead looks at the right hand side of the assignment for a list of values, and assigns the elements of the list in order. It’s just as if you did this:

a,b,c = 1,2,3

which assigns 1 to a, 2 to b, and 3 to c. Inserting a function call doesn’t change the semantics:

def foo():
    return 1,2,3

a,b,c = foo() # same result

If you try to use it to assign the same value to multiple variables, you get an error:

a,b,c = 1
#=> TypeError: cannot unpack non-iterable int object

The only way to do that is to repeat the value on the right as many times as there are variables on the left, like this:

a,b,c = 1,1,1

or this:

a,b,c = [1]*3

Answered By: Mark Reed

Assign a function to multiple variables

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