Question

I’m printing a stat block for a game character object. In a previous question I was demonstrated a way to display the object data using in the __str__ function like so:

def __str__(self):
    if self.poisoned is True:
        status = "[POISONED]"
    else:
        status = ""
    self.status = status
    return ('NAME: {name} {status}\n' \
            'XP:   {xp}\n' \
            'HP:   {hit_points}\n' \
            'SP:   {spell_points}\n' \
            'STR:  {strength}\n' \
            'DEX:  {dexterity}\n' \
            'WEAPON: {weapon}\n' \
            'SPELL:  {spell}\n' \
            'ITEM:   {item}\n' \
            'AURA:   {aura}\n' \
            ).format(**self.__dict__)

The problem I want to solve has to do with the WEAPON, SPELL, ITEM and AURA variables. These items are defined in the Character object as single item lists: weapon=[] and so on. Using the above method returns the list object instead of the object it contains without the []. I’d rater see a blank " " string or the list’s contained object if one exists and not [].

NAME: Bones 
XP:   0
HP:   100
SP:   100
STR:  14
DEX:  19
WEAPON:   []
SPELL:    []
ITEM:     []
AURA:     []

I’ve tried a number of experiments including replacing the {weapon} reference with {current_weapon} after defining current_weapon = weapon[0] which won’t work if the list object is empty. That just errors with IndexError: list index out of range. I could generate the items at object instantiation, but that won’t work as self.item will at times be an empty list container.

I could propagate the lists with " " objects but would then have to juggle them out with replacement items and keep track of this which seems very inelegant and potentially cumbersome.

I just can’t seem to wrap my head around an elegant way to print the list object in the above __str__ return as currently designed. I’m still learning Python and want to believe there is a simple addition I could append to this return string to do this.

Answer 1

You could just create a local copy of your dict, and modify the values you want, before passing that on to the format:

def __str__(self):
    local_data = self.__dict__.copy()

    local_data['status'] = "[POISONED]" if self.poisoned else ""

    local_data['weapon'] = " " if not self.weapon else ','.join(self.weapon)

    return ('NAME: {name} {status}\n' \
            'XP:   {xp}\n' \
            'HP:   {hit_points}\n' \
            'SP:   {spell_points}\n' \
            'STR:  {strength}\n' \
            'DEX:  {dexterity}\n' \
            'WEAPON: {weapon}\n' \
            'SPELL:  {spell}\n' \
            'ITEM:   {item}\n' \
            'AURA:   {aura}\n' \
            ).format(**local_data)

It is probably better to do that, than to modify your attributes simple for the formatting, like you were doing with your self.status. Now you are just modifying temp copies.