Python List as variable name [duplicate]

Question

I've been playing with Python and I have this list that I need worked out. Basically I type a list of games into the multidimensional array and then for each one, it will make 3 variables based on that first entry.

Array that is made:

Applist = [
['Apple', 'red', 'circle'],
['Banana', 'yellow', 'abnormal'],
['Pear', 'green', 'abnormal']
]

For loop to assign each fruit a name, colour and shape.

for i in Applist:
    i[0] + "_n" = i[0]
    i[0] + "_c" = i[1]
    i[0] + "_s" = i[2]

When doing this though, I get a cannot assign to operator message. How do I combat this?

The expected result would be:

Apple_n == "Apple"
Apple_c == "red"
Apple_s == "circle"

Etc for each fruit.

Possible duplicate: How do I create a variable number of variables? This answer covers dicts, and this one covers named tuples. — wjandrea
– wjandrea, Commented Jul 2, 2020 at 0:17
@wjandrea - Your second link is a question asked 4 years after this one. Combining both does cover this but marking it as a duplicate when the second was asked 4 years after this one doesn't make sense to me. — Skowt
– Skowt, Commented Jul 2, 2020 at 9:11
Older questions can be closed as duplicates of newer questions — wjandrea
– wjandrea, Commented Jul 2, 2020 at 12:47

Lauritz V. Thaulow · Accepted Answer · 2012-06-20 11:56:45Z

24

This is a bad idea. You should not dynamically create variable names, use a dictionary instead:

variables = {}
for name, colour, shape in Applist:
    variables[name + "_n"] = name
    variables[name + "_c"] = colour
    variables[name + "_s"] = shape

Now access them as variables["Apple_n"], etc.

What you really want though, is perhaps a dict of dicts:

variables = {}
for name, colour, shape in Applist:
    variables[name] = {"name": name, "colour": colour, "shape": shape}

print "Apple shape: " + variables["Apple"]["shape"]

Or, perhaps even better, a namedtuple:

from collections import namedtuple

variables = {}
Fruit = namedtuple("Fruit", ["name", "colour", "shape"])
for args in Applist:
    fruit = Fruit(*args)
    variables[fruit.name] = fruit

print "Apple shape: " + variables["Apple"].shape

You can't change the variables of each Fruit if you use a namedtuple though (i.e. no setting variables["Apple"].colour to "green"), so it is perhaps not a good solution, depending on the intended usage. If you like the namedtuple solution but want to change the variables, you can make it a full-blown Fruit class instead, which can be used as a drop-in replacement for the namedtuple Fruit in the above code.

class Fruit(object):
    def __init__(self, name, colour, shape):
        self.name = name
        self.colour = colour
        self.shape = shape

edited Jun 20, 2012 at 11:56

answered Jun 20, 2012 at 11:31

Lauritz V. Thaulow

51.3k13 gold badges76 silver badges94 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Skowt Over a year ago

Thanks @lazyr, That was a very quick solution :) I just have one more question... if now you had for name, colour, shape in Applist: variables[name] = shape. Would that change the name in Applist, or would that create a new variable and not touch the Applist?

Lauritz V. Thaulow Over a year ago

@Skowt Applist and variables are wholly independent after this code has run, and anything done to one of them will not affect the other.

Skowt Over a year ago

Just thought I'd say thanks to @lazyr for answering my second questions ;)

mVChr · Accepted Answer · 2012-06-20 11:32:17Z

2

It would be easiest to do this with a dictionary:

app_list = [
    ['Apple', 'red', 'circle'],
    ['Banana', 'yellow', 'abnormal'],
    ['Pear', 'green', 'abnormal']
]
app_keys = {}

for sub_list in app_list:
    app_keys["%s_n" % sub_list[0]] = sub_list[0]
    app_keys["%s_c" % sub_list[0]] = sub_list[1]
    app_keys["%s_s" % sub_list[0]] = sub_list[2]

answered Jun 20, 2012 at 11:32

mVChr

50.3k11 gold badges111 silver badges105 bronze badges

Collectives™ on Stack Overflow

Python List as variable name [duplicate]

2 Answers 2

3 Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Linked

Related