Why is this code wrong?
Isn't D a global variable?
import pandas as pd
D = pd.DataFrame()
D['z'] = [2]
def funz2(z):
d = pd.DataFrame()
d['z'] = z
D = D.append(d)
print(D)
print(funz2(4))
This is the error message
In [22]: ---------------------------------------------------------------------------
UnboundLocalError Traceback (most recent call last)
<ipython-input-22-68bb930462f5> in <module>()
----> 1 __pyfile = open('''/tmp/py3865JSV''');exec(compile(__pyfile.read(), '''/home/donbeo/Desktop/prova.py''', 'exec'));__pyfile.close()
/home/donbeo/Desktop/prova.py in <module>()
14
15
---> 16 print(funz2(4))
/home/donbeo/Desktop/prova.py in funz2(z)
10 d = pd.DataFrame()
11 d['z'] = z
---> 12 D = D.append(d)
13 print(D)
14
UnboundLocalError: local variable 'D' referenced before assignment
EDIT: If variables are not automatically global. Why does it work?
x = 3
def funz(z):
return z * x
print(funz(4))
Your funz2 can certainly access the D variable that you declared outside of it.
The problem you see is because you have declared another D variable local to the funz function with the line that starts with D=. This local one takes precedence over the other globalish one and thus you get the exception.
What you can do is as Alex Woolford suggests and declare the D in the funz function as global using the global statement in effect saying 'see that D there, I don't wanna declare no local D var there I want it to reference that other global one'.