TypeError: 'NoneType' object is not iterable in Python

python nonetype
Alex Gordon picture Alex Gordon · Oct 8, 2010 · Viewed 634.7k times · Source

What does error TypeError: 'NoneType' object is not iterable mean?

I am getting it on this Python code:

def write_file(data, filename): # creates file and writes list to it
  with open(filename, 'wb') as outfile:
    writer = csv.writer(outfile)
    for row in data: # ABOVE ERROR IS THROWN HERE
      writer.writerow(row)

Answer

vanza picture vanza · Oct 8, 2010

It means the value of data is None.

Related questions

Why do I get AttributeError: 'NoneType' object has no attribute 'something'?

I keep getting an error that says AttributeError: 'NoneType' object has no attribute 'something' The code I have is too long to post here. What general scenarios would cause this AttributeError, what is NoneType supposed to mean and how can …

Read More
Python `if x is not None` or `if not x is None`?

I've always thought of the if not x is None version to be more clear, but Google's style guide and PEP-8 both use if x is not None. Is there any minor performance difference (I'm assuming not), and is there …

Read More
not None test in Python

Out of these not None tests. if val != None: if not (val is None): if val is not None: Which one is preferable, and why?

Read More