if else in a list comprehension
Do-something if <condition>, else do-something else.
list
How do I concatenate two lists in Python?
You can use the + operator to combine them: Output:
Writing a list to a file with Python
You can use a loop: In Python 2, you can also use If you’re keen on a single function call, at least remove the square brackets [], so that the strings to be printed get made one at a time (a genexp rather than a listcomp) — no reason to take up all the memory required … Read more
Finding the average of a list
On Python 3.4+ you can use statistics.mean() On older versions of Python you can do On Python 2 you need to convert len to a float to get float division There is no need to use reduce. It is much slower and was removed in Python 3.
How to avoid “RuntimeError: dictionary changed size during iteration” error?
In Python 3.x and 2.x you can use use list to force a copy of the keys to be made: In Python 2.x calling keys made a copy of the keys that you could iterate over while modifying the dict: But note that in Python 3.x this second method doesn’t help with your error because … Read more
How to avoid “RuntimeError: dictionary changed size during iteration” error?
In Python 3.x and 2.x you can use use list to force a copy of the keys to be made: In Python 2.x calling keys made a copy of the keys that you could iterate over while modifying the dict: But note that in Python 3.x this second method doesn’t help with your error because … Read more
Python: finding an element in a list [duplicate]
The best way is probably to use the list method .index. For the objects in the list, you can do something like: with any special processing you need. You can also use a for/in statement with enumerate(arr) Example of finding the index of an item that has value > 100. Source
Check if something is (not) in a list in Python
The bug is probably somewhere else in your code, because it should work fine: Or with tuples:
Converting array to list in Java
In your example, it is because you can’t have a List of a primitive type. In other words, List<int> is not possible. You can, however, have a List<Integer> using the Integer class that wraps the int primitive. Convert your array to a List with the Arrays.asList utility method.
appending list but error ‘NoneType’ object has no attribute ‘append’
I have a script in which I am extracting value for every user and adding that in a list but I am getting “‘NoneType’ object has no attribute ‘append’”. My code is like I want to add last name in list. If its none then dont add it in list . Please help Note:p is … Read more