• the parameter should be named file_name, the input_file woould be reserved to the real file-

• instead of doing
  
  inputfile = open(input_file, "r")

better use

with open(file_name, "r") as input_file:
     #use input_file inside the block
 #here the file is magically closed

It's named context manager and it's good and modern way to open file see http://eigenhombre.com/2013/04/20/introduction-to-context-managers/ for explanations

• actually the standard of python is snake_case, so: row_num, col_num, input_file.
• instead of counting the rows using the following pattern:
  
  headers = next(reader) for row in reader: #do what you want with the data row

this function don't look really necessary. json.dumps() should be inlined where it is called

• better use os.path.basename()
• use output_file (snake_case)
• use the with idiom

use the if __name__ == "main" idiom see: https://docs.python.org/3/tutorial/modules.html#executing-modules-as-scripts