How to attach i in 'for i in range(x)' to a label in python?

Don't build dynamic variables; keep your data out of your variables. Build a list or dictionary instead.

With a dictionary, for example, it'd be:

card_labels = {}for i in range(2):    for j in range(6):        label = CardLabel(root)        label.grid(row=i, column=j)        label.configure(image=CardLabel.blank_image)        card_labels[i, j] = label

This stores the labels keyed on the (i, j) tuple in the card_labels dictionary.

You could try using dictionary, like this:

cardlabels = {}for i in range(2):    for j in range(6):        label = str(i)+'.'+str(j)        cardlabels[label] = CardLabel(root)        cardlabels[label].grid(row=i, column=j)        cardlabels[label].configure(image=CardLabel.blank_image)

Now they will be labeled cardlabels['1.1'], cardlabels['1.2']..

While I definitely recommend using either a dictionary or list solution, if you have your heart set on using variables, something like this should do the trick.

for i in range(2):    for j in range(6):        vars()['cardlabel%d%d' % (i,j)] = CardLabel(root)        vars()['cardlabel%d%d' % (i,j)].grid(row=i, column=j)        vars()['cardlabel%d%d' % (i,j)].configure(image=CardLabel.blank_image)