TypeError: only integer scalar arrays can be converted to a scalar index in pythn code example

Example 1: TypeError: only size-1 arrays can be converted to Python scalars

You are getting the error "only length-1 arrays can be converted to 
"Python scalars" is because when the function expects a single value instead of that you have passed an array.

Example 2: only integer scalar arrays can be converted to a scalar index pandas

df1 = pd.DataFrame({'a': [1, 2]})
df2 = pd.DataFrame({'b': [3, 1]})

df1.columns = ['b']

df1.merge(df2, on='b')
#   b
# 0 1