use/execute a string within a list as an object name (python)

Question

It looks like this:

I define a class:

class Boy():
    def __init__(self):
        self.age    = input()
        self.height = input()

Then I define a list with the names of the boys that I want to be object instances of the above 'class Boy':

boys = [input(), input()]

(for example: john & frank, so that boys = ['john', 'frank'])

I want now to iterate over my list 'boys' and use each name to make an object of the 'class Boy':

for value in boys:
    value = Boy()

Of course, it does not work :-) but is there a way to achieve it ?? I have been using Python since 1 week, if the question sounds silly :-) If someone could help me, will be very thankful

Thank you all for the help, I implemented the proposed solutions:

thank_you_people = ['Makoto','L3viathan','Rcynic','Pythonic','Paul Rooney', 'st.eve']

:-)

for person in thank_you_people:
print('Thank you, %s' % person)

Answer 1

I would highly recommend changing your class up a bit, to remove input() calls from the constructor. You could use an __init__ method that has optional arguments for age and height, and a forced one for name:

class Boy():
    def __init__(self, name, age=None, height=None):
        self.age    = age
        self.height = height
        self.name   = name

You then can instantiate with a name, and assign the attributes later:

boys = [Boy(input("New boy: ")), Boy(input("New boy: "))] # e.g. "John", "Frank"
for boy in boys:
    boy.age = input("Age of",boy.name + "?")
    boy.height = input("Height of",boy.name + "?")

edit: To have the boys in a dictionary for easier access:

boys = {}
for _ in range(2):
    name = input("New boy:")
    boys[name] = Boy(name)
for boy in boys:
    boys[boy].age = input("Age of",boys[boy].name + "?")
    boys[boy].height = input("Height of",boys[boy].name + "?")

Answer 2

To not use just anything as an object name, you can use the input as keys for a dict. Something like this:

    class Boy():
        def __init__(self):
            self.age = input()
            self.height = input()

    boys = [input(), input()] # this is probably a bad idea

    b = {}
    for boy in boys:
        b[boy] = Boy()

Answer 3

I'd suggest to i) use a dictionary for creating variables with the name contained in a string and ii) pass age and height as args, **kwargs or *args in the class, as already suggested by Makoto. Something along these lines:

class Boy():
    def __init__(self, name, age=0, height=0):
        self.age    = age
        self.height = height

boys = ['finn', 'jake']
ages = [16, 33]
height = [165, 120]

boys_objects = {}

for i, b in enumerate(boys):
    boys_objects[b] = Boy(age=ages[i], height=heights[i]) 

Answer 4

Don't use the input function in your __init__ method, as it restricts how your Boy class can be used. Instead define a separate function that creates a Boy and pass those parameters to your Boy constructor. Then you could store your Boys in a dict, keyed by the boys name.

e.g.

class Boy():
    def __init__(self, age, height):
        self.age    = age
        self.height = height
    def __str__(self):
        return 'age=%d height=%d' % (self.age, self.height)

def create_boy(name):
    age = int(input('enter age for %s: ' % name))
    height = int(input('enter height for %s: ' % name))
    return Boy(age, height)

boynames = []

while(True):
   name = input('enter boy name: ')      
   if name == '':
       break
   boynames.append(name)

boys = {}
for boyname in boynames:
    boys[boyname] = create_boy(boyname)

for name, boyinfo in boys.items():
    print('name=%s %s' % (name, boyinfo))

Later on you could query a particular boys name like so

if 'paul' in boys:
    print(boys['paul'].age)
    print(boys['paul'].height)
else:
    print('no boy called paul')

This isn't designed to work if you can have Boys with the same name. In that case you could have each dictionary entry hold a list of Boys and find some other parameter to distinguish between the Boys of the same name.

Answer 5

Use the zip function. You'll have to change your class constructor a little bit though.

class Boy(object):
    def __init__(self, (name, age, height)):
        self.name = name
        self.age = age
        self.height = height

Then get the input values into lists

names = ['a','b','c']
ages = [10, 20, 30]
heights = [155, 160, 165]
boys = zip(names, ages, heights)
for guy in boys:
    b = Boy(guy)
    print b.name, b.age, b.height

I don't know wha you want to do with the objects - but you can change that in the for loop.

EDIT: In response to the error OP is getting in the comments:

I cannot reproduce the init error. I tried with python and iPython both. Alternatively you could try

def __init__(self, guy_tuple):
    self.name = guy_tuple[0]
    self.age = guy_tuple[1]
    self.height = guy_tuple[2]

If that doesn't work either, you can change the constructor to take in name, age and height individually. Like is working for you.

def __init__(self, name, age, height):
    self.name = name
    ... 

then the for loop must change accordingly. Since guy is a tuple with all three elements, you'll have to get each one by index within the tuple.

for guy in boys:
    b = Boy(guy[0], guy[1], guy[2])

Yes object b will be overwritten, you'll have to change it to do what you need it to do once you get the object. So after b is instantiated, pass it to another function to do what you want with it, or append it to a list. Once b is an object, you continue with the logic you want.