Sending files between operators

I'm not sure I understand what you want to do. Send flat files? There are different data loaders for flat files, databases, HDFS, etc.

So, I want to read a text file using one operator, read a file for example, and then send files in a loop to process each one separately(Text processing,i.e, stemming, tokenize, etc.). The way I understand, the operators can communicate only using Pandas Dataframe objects. 

If I have written a python script on the Python script operator which would take a file as an input, I'm unable to pass the file from read file operator.

Only the Execute Python operator works Panda Dataframes. Other RapidMiner operators do not depend on Pandas, they have their own internal file handling.