Can't append NaN to python list - python-3.x

Question

The error is
Traceback (most recent call last):
File "1.py", line 28, in <module>
buy.append(np.nan)
AttributeError: 'numpy.ndarray' object has no attribute 'nan'
Here the code its python 3
import fxcmpy
import socketio
from pylab import plt
import numpy as np
from finta import TA
TOKEN='xxxx'
con = fxcmpy.fxcmpy(access_token=TOKEN, log_level='error', server='real', log_file='log.txt')
#print(con.get_instruments())
data = con.get_candles('US30', period='D1', number=250)
con.close()
df1=data[['askopen','askhigh', 'asklow', 'askclose']]
plt.style.use('seaborn')
np=df1.to_numpy()
df2=df1.rename(columns={'askopen':'open','askhigh':'high','asklow':'low','askclose':'close'})
dfhma=TA.HMA(df2,14)
pr1=dfhma.shift(1)
pr2=dfhma.shift(2)
buy=[]
sell=[]
i=0
flag=''
for item in dfhma:
if item > pr1[i] and item > pr2[i] and flag!=1:
flag=1
buy.append(item)
else:
buy.append(np.nan)
if item < pr1[i] and item < pr2[i] and flag!=0:
flag=0
sell.append(item)
else:
sell.append(np.nan)
i=i+1
print(buy)
print('buy len='+str(len(buy)))
mk=[]
for item in dfhma:
print(item)
plt.plot(dfhma)
plt.scatter(dfhma.index,buy,marker='^',color='g')
plt.scatter(dfhma.index,sell,marker='v',color='r')
plt.show()
Search Google/Stackoverflow nothing was found and change nan to NaN,NAN still got the same error guessing its newbie error Help !! Just try to add NaN to the list as a buy/sell signal and it doesn't work what could be wrong here ?

Answer 1

In line 14 np=df1.to_numpy() you reassigned variable np from a package to a numpy array. So when you called np.nan it was searching nan from the numpy ndarray instance, not the package.
Change the variable to any other name and it will work fine.