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21 Ιουλ 2010 · To loop over both key and value you can use the following: For Python 3.x: for key, value in d.items(): For Python 2.x: for key, value in d.iteritems(): To test for yourself, change the word key to poop. In Python 3.x, iteritems() was replaced with simply items(), which returns a set-like view backed by the dict, like iteritems() but even
Notice that the index runs from 0. This kind of indexing is common among modern programming languages including Python and C. If you want your loop to span a part of the list, you can use the standard Python syntax for a part of the list. For example, to loop from the second item in a list up to but not including the last item, you could use
Use break and continue to do this. Breaking nested loops can be done in Python using the following: for a in range(...): for b in range(..): if some condition: # break the inner loop break else: # will be called if the previous loop did not end with a `break` continue # but here we end up right after breaking the inner loop, so we can # simply break the outer loop as well break
30 Απρ 2012 · I don't understand why some answers are complicated. This is how I would do it with Python 2.7. Replace DIRECTORY_TO_LOOP with the directory you want to use. import os DIRECTORY_TO_LOOP = '/var/www/files/' for root, dirs, files in os.walk(DIRECTORY_TO_LOOP, topdown=False): for name in files: print(os.path.join(root, name))
This for loop iterates over all elements in a list: for item in my_list: print item Is there a way to know within the loop how many times I've been looping so far? For instance, I want to take a list and after I've processed ten elements I want to do something with them. The alternatives I thought about would be something like:
You could set a variable in the inner loop, and check it in the outer loop immediately after the inner loop exits, breaking if appropriate. I kind of like the GOTO method, provided you don't mind using an April Fool's joke module - it’s not Pythonic, but it does make sense.
A for loop in Python is syntactic sugar for handling the iterator object of an iterable an its methods ...
The full code is available to download and run in my python/pandas_dataframe_iteration_vs_vectorization_vs_list_comprehension_speed_tests.py file in my eRCaGuy_hello_world repo. Here is the code for all 13 techniques: Technique 1: 1_raw_for_loop_using_regular_df_indexing
You can save some of that manual 2d array traversal: in the definition of the loop, zip together the column names and axs.flatten(): for col, ax in zip(df.columns, axs.flatten():, and then the lines in the loop are ax.scatter, ax.set_ylabel.
24 Οκτ 2008 · In Python-speak, an iterable is any object which "understands the concept of a for-loop" like a list [1,2,3], and an iterator is a specific instance of the requested for-loop like [1,2,3].__iter__(). A generator is exactly the same as any iterator, except for the way it was written (with function syntax).
