为什么这会引起缩进错误？

Question

for bucketLabel, eventList in test_source_json.iteritems(): 
    if bucketLabel == "spotlight": 
        for event in eventList: 
            try: 
                for key in source_keys: 
                    if key not in event: 
                        if key not in responseDictionary[currentTestName][url]: 
                            responseDictionary[currentTestName][url][key] = list()
                        responseDictionary[currentTestName][url][key].append(event)
            except: 
                exc_type, exc_obj, exc_tb = sys.exc_info()
                logging.info("caught exception %s, and obj %s at line number %s" % (exc_type, exc_obj, exc_tb.tb_lineno))
                continue    

This code throws an indentation error at line 4 try: http://repl.it/N7W illustrates the error

Totally confused as to why.

Answer 1

你在那条线上使用制表符而不是空格

Answer 2

The problem—as it often is in cases like this—is that you're mixing tabs and spaces.

Lines 2 and 3 are indented with tabs; line 3 starts with two tab characters. That presumably looks like 8 spaces in your text editor, but as far as Python is concerned, it's 16 spaces.

Line 4 is indented with 12 spaces. So, in your editor, it looks more indented than line 3. But to Python, it's less indented. Hence the error.

The solution is to always use spaces, never tabs. (Alternatively, you can always use tabs instead, just so long as you don't mix them… but always spaces is easier and better in many ways.)

Most editors can be configured to do this—and to show tabs distinctly differently from spaces. The ones that can't (like Notepad) probably shouldn't be used for programming.

You should also run Python with the -t or -tt flag to diagnose IndentationError s, because it will tell you that you're using tabs and spaces inconsistently. The tabnanny module/script can also be helpful.

Answer 3

Python requires that you use either tabs or spaces for indentation and not both. The official Python recommendation is to use four spaces rather than a tab, but what's more important is you must use the same on each line.