Python: Check if a variable is NA in the if statement-CodePudding

I have a function that looks like this:

if (Var_A   Var_B <7):
    Do something ...

The issue is, the Var_B column in the dataframe has either integers, or NaN values.

If I write the function as it is now, it is returning error as "TypeError: boolean value of NA is ambiguous".

How should I re-write the function so that, if Var_B is NaN, just skip the comparison and return Var_A?

Is it something like:

if Var_B is not null:
 if (Var_A   Var_B <7):
    Do something ...
 else:
    Var_A

Or, I can do something more elegant without adding an if statement:

if (Var_A   Var_B < 7) and (Var_B is not null):
   Do something ...

Additionally, how exactly do I write the syntax that checks Var_B is not null? I tried to write != isnull() and !is.na() but both are not working..

Very new to Python, much appreciation for your help!

CodePudding user response：

IIUC use if working with scalars:

Var_A = 1
Var_B = 2

if (Var_A   Var_B < 7) and pd.notna(Var_B):
    print ('pass')
    
pass
    
Var_A = 1
Var_B = np.nan

if (Var_A   Var_B < 7) and pd.notna(Var_B):
    print ('pass')

If working with columns ouput is boolean mask, code is changed:

df = pd.DataFrame({'Var_A':[1,2,3], 'Var_B':[np.nan, 2, 7]})

print (df)
0    False
1     True
2    False
dtype: bool

mask = ((df.Var_A   df.Var_B) < 7) & df.Var_B.notna()
print (mask)
0    False
1     True
2    False
dtype: bool

But then if mask: cannot be used, because using array.

More infotmation in link

CodePudding user response：

Pandas has the isnull function that returns True or False if the column's item is Nan or no Nan. So try doing it this way

if not Var_B.isnull().values.any():
    if (Var_A   Var_B <7):
        Do something ...
else:
    Var_A

CodePudding user response：

simply do

df = df.fillna(0) 
# if you want to get rid of all NaN values and replace with 0

(or)

df['DataFrame Column'] = df['DataFrame Column'].fillna(0) 
# if you only want to replace NaN in a particular column to 0

Now you can proceed with adding/subtracting/ whatever you want to do.

CodePudding user response：

You could also try something like this, it usually works for me:

def func(a,b):
  
  try:
    check = np.isnan(b) 
    if check == True:
      print("B is nan")
      print(int(a))
    else:
      np.sum(a b)
      if a b<7:
          print("Something")
  except TypeError:
    print("Error")
  

for x in .....:
  for y in .....:
    func(x,y)