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Given the piece of code:
from glob import glob, iglob for fn in glob('/*'): print fn print '' for fn in iglob('/*'): print fn Reading the documentation for glob I see that glob() returns a basic list of files and iglob an Iterator. However I'm able to iterate over both and the same list of files is returned by each of them.
I've read the documentation on Iterator but it hasn't shed anymore light on the subject really!
So what benefit does iglob() returning an Iterator provide me over the list from glob()? Do I gain extra functionality over my old friend the lowly list?
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Using Glob() function to find files recursively We can use the function glob. glob() or glob. iglob() directly from glob module to retrieve paths recursively from inside the directories/files and subdirectories/subfiles. Syntax: glob.glob(pathname, *, recursive=False) glob.iglob(pathname, *, recursive=False)
The glob API iglob(pathname, recursive=False) Same as glob. glob , except that it returns an iterator, meaning that not all values get stored in memory - so can be much more efficient. glob. escape(pathname) Escapes special characters in the passed in “pathname”.
An iterator is an object that contains a countable number of values. An iterator is an object that can be iterated upon, meaning that you can traverse through all the values. Technically, in Python, an iterator is an object which implements the iterator protocol, which consist of the methods __iter__() and __next__() .
The __iter__() method returns the iterator object itself. If required, some initialization can be performed. The __next__() method must return the next item in the sequence. On reaching the end, and in subsequent calls, it must raise StopIteration .
The difference is mentioned in the documentation itself:
Return an iterator which yields the same values as glob() without actually storing them all simultaneously.
Basically list will have all the items in memory. Iterator need not, and hence it requires less memory.
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Adding to amit's answer. iglob() is useful in the particular case where if you delete a directory in the list, the files and folders in the list will be stored by glob() and hence further access in the loop throws exception. But by using iglob() we can overcome the concurrent modification exception
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