Why does second iteration always fail? - python-3.x

Question

I am trying to create a dict of z_scores by filtering a dataframe based upon five locations.
No matter which location is first in the list, I always get the first key:value pair placed into
the dict, and no matter which location is second, I always get this error:
Traceback (most recent call last):
File "C:\Program Files\JetBrains\PyCharm 2018.2.1\plugins\python\helpers\pydev\pydevd.py", line 1434, in _exec
pydev_imports.execfile(file, globals, locals) # execute the script
File "C:\Program Files\JetBrains\PyCharm 2018.2.1\plugins\python\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile
exec(compile(contents+"\n", file, 'exec'), glob, loc)
File "C:/Users/Mark/PycharmProjects/main/main.py", line 104, in <module>
z_score = z_score(base, df['SalePrice'])
TypeError: 'numpy.float64' object is not callable
Since every list value works when it is first, I don't see why every subsequent iteration fails.
My code:
def z_score(val, array, bessel=0):
mean = array.mean()
st_dev = std(array, ddof=bessel)
distance = val - mean
z = distance / st_dev
return z
neighborhoods = ['NAmes', 'CollgCr', 'OldTown', 'Edwards', 'Somerst']
base = 200000
z_scores = {}
for neighborhood in neighborhoods:
df = houses.loc[houses['Neighborhood'] == neighborhood]
z_score = z_score(base, df['SalePrice'])
z_scores[neighborhood] = z_score
sorted_z_scores = sorted(z_scores.items(), key=lambda x: x[1], reverse=True)
print(sorted_z_scores)

Answer 1

In python, the interpreter puts a higher priority on your variable names in the local scope than method names, so when you use z_score as a variable name, it masks access to the z_score method name, if you change the name of your z_score variable, your code should run.