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.")

Answer 1

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

Answer 2

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)