What is the error in this Python code?

Question

This one's the program to calculate the frequency in an array. Here I'am getting the error that global name "mod" is not defined. Look at:: tempr=mod(self.a[i]) , where I am using it and the function mod has been written in a different function. Please help me in correcting this function.

class abc:
 def __init__(self):
 self.n=0
 self.a=[]
 def read(self):
 self.n=input()
 for i in range(0,self.n):
 temp=input()
 self.a.append(temp)
 def freq(self):
 max=self.a[0]
 for i in range(0,self.n):
 tempr=mod(self.a[i])
 if tempr>max:
 max=tempr
 tempa=[0]*(2*(max)+1)
 bb=[0]*self.n
 for j in range(0,self.n):
 if(self.a[j]>=0):
 tempa[self.a[j]]=tempa[self.a[j]]+1
 else:
 tempa[max-self.a[j]]=tempa[max-self.a[j]]+1
 for i in range(0,self.n):
 if bb[self.a[i]]==0:
 if self.a[i]>=0:
 print "%d : %d " % (self.a[i],tempa[self.a[i]]) 
 bb[self.a[i]]=bb[self.a[i]]+1
 else:
 print "%d : %d " % (self.a[i],tempa[max-self.a[i]])
 bb[self.a[i]]=bb[self.a[i]]+1
 def mod(y):
 if y>=0:
 return y
 else:
 return y
k=abc()
k.read()
k.freq()

• jwodder: mod(y) always returns y. Doesn't seem very useful to me....

Answer 1

There are two issues in your code:

1. It seems that you want your mod to be a static method. Non-static method should always have self as a first argument.

2. Even if mod is a static method, you need to call it as abc.mod.

Two ways to solve it:

1. Make mod a global function instead of a method (just indent its definition 4 spaces to the left)

or

2. Make it a static method by prepending it with @staticmethod and call it as abc.mod:

...
 tempr=abc.mod(self.a[i])
... 
@staticmethod
def mod(y):
 if y>=0:
 return y
 else:
 return y

Also note that mod should probably return -y if y < 0