python-'str' abject has no attribute 'scatter' - string

Question

I need to plot a 7x7 scatterplot diagram by metplotlib.pyplot (no seaborn at this moment). I try to make it semi automatics, so I use an array of ax names ax11, ax12, ......, ax77 to present the subplots. mean while when I use them to call scatter, it is rejected, I think python recognize them as strings but not keywords for the subplot. The Error Message is "AttributeError: 'str' object has no attribute 'scatter'". Here is the part of the code:
import matplotlib.pyplot as plt
import numpy as np
characters = ['A','B','C','D','E','F']
box = dict(facecolor ='yellow', pad = 5, alpha = 0.2)
fig, ((ax11,ax12,ax13,ax14,ax15,ax16,ax17),\
(ax21,ax22,ax23,ax24,ax25,ax26,ax27),\
(ax31,ax32,ax33,ax34,ax35,ax36,ax37),\
(ax41,ax42,ax43,ax44,ax45,ax46,ax47),\
(ax51,ax52,ax53,ax54,ax55,ax56,ax57),\
(ax61,ax62,ax63,ax64,ax65,ax66,ax67),\
(ax71,ax72,ax73,ax74,ax75,ax76,ax77),\
) = plt.subplots(7,7)
fig.subplots_adjust(left = 0.2, wspace =0.2,)
fig.tight_layout(pad=1, w_pad=2, h_pad=4.0)
st = fig.suptitle("Scatterplot diagram", \
fontsize="x- large")
for i in range(7):
for j in range(7):
no_ax = str(i)+str(j)
nm_ax = "ax"+str(no_ax)
nm_ax.scatter(data[caracters[i]],data[caracters[i]])
nm_ax.set_title('xy')
nm_ax.set_xlabel('x')
nm_ax.set_ylabel('y')
continue
st.set_y(0.95)
fig.subplots_adjust(top=0.85)
plt.show()
I believe there is a method to convert the string to a right format, but I do not know how. Please help. Thanks.

Answer 1

In general the approach of building variable names from strings should be avoided. While this can be done using the eval function, it's not even necessary.
The problem lies in the lines
no_ax = str(i)+str(j) #this is a string
nm_ax = "ax"+str(no_ax) # this is still a string
nm_ax.scatter(data[caracters[i]],data[caracters[i]])
# a string cannot be plotted to
A string does not have a scatter method. What you need is the axes object to which you plot.
A solution is to just use the axes that are created in the call to plt.subplots()directly in the loop.
import matplotlib.pyplot as plt
import numpy as np
fig, axes = plt.subplots(ncols=7,nrows=7)
for i in range(7):
for j in range(7):
axes[i,j].scatter(np.random.rand(5),np.random.rand(5))
axes[i,j].set_title('{},{}'.format(i,j))
plt.show()