有关“ for”循环的一般问题

Question

I'm beginning to learn Python by following an introductory text and have come across an exercise that implements a for loop to read files from a directory. I've used for loops before in R and Java and I have some questions. I'm hoping the community could help me wrap my head around about for loops in general.

1. It seems (in Python at least) that special characters and numbers can't be used as the "name" in loop. What's the reason for this?

   ex:

    for @ in data: print (@, end= ' ') 

   will produce an error. However replacing @ with x or name for example is fine. Is this one of those things we accept, don't question, and move on?

2. How does the for loop know (or evaluate) whether an object is "iterable"?

Answer 1

1. As others have mentioned, see the rules for Python variable, ie identifier, names: https://docs.python.org/3/reference/lexical_analysis.html#identifiers

2. An object is iterable if it has the __next__() method defined . See also https://wiki.python.org/moin/ForLoop