There is no where statement but you can “emulate” it using for: a=[0] def f(x): a[0] += 1 return 2*x print [ (x, y) for x in range(5) for y in [f(x)] if y != 2 ] print “The function was executed %s times” % a[0] Execution: $ python 2.py [(0, 0), (2, 4), (3, … Read more
tqdm Using the tqdm package, a fast and versatile progress bar utility pip install tqdm from tqdm import tqdm def process(token): return token[‘text’] l1 = [{‘text’: k} for k in range(5000)] l2 = [process(token) for token in tqdm(l1)] 100%|███████████████████████████████████| 5000/5000 [00:00<00:00, 2326807.94it/s] No requirement 1/ Use a side function def report(index): if index % 1000 … Read more
Add an if into your comprehension like: l = [y for y in (f(x) for x in [1,2,3,4]) if y is not None] By placing a Generator Expression inside the list comprehension you will only need to evaluate the function once. In addition the generator expression is a generator so takes no extra intermediate storage. … Read more
The main logic of creating a function is to isolate the comprehension’s iteration variablepeps.python.org. By creating a function: Comprehension iteration variables remain isolated and don’t overwrite a variable of the same name in the outer scope, nor are they visible after the comprehension However, this is inefficient at runtime. Due to this reason, python-3.12 implemented … Read more
forEach is effectively built in: a = [‘a’,’b’,’c’] for el,i in a alert “Element #{el} is at index #{i}”
Cleaner Pythonic approach: >>> [(x,y) for x,y in zip(myList, myList[1:]) if y == 9] [(8, 9), (4, 9), (7, 9)] What is the code above doing: zip(some_list, some_list[1:]) would generate a list of pairs of adjacent elements. Now with that tuple, filter on the condition that the second element is equal to 9. You’re done … Read more
The very definition of a list comprehension is to produce one list object. Your 2 list objects are of different lengths even; you’d have to use side-effects to achieve what you want. Don’t use list comprehensions here. Just use an ordinary loop: listOfA, listOfB = [], [] for idx, x in enumerate(s): target = listOfA … Read more
You can use zip with * to get transpose of a matrix: >>> A = [[ 1, 2, 3],[ 4, 5, 6]] >>> zip(*A) [(1, 4), (2, 5), (3, 6)] >>> lis = [[1,2,3], … [4,5,6], … [7,8,9]] >>> zip(*lis) [(1, 4, 7), (2, 5, 8), (3, 6, 9)] If you want the returned list … Read more
Just use sum checking if each object is not None which will be True or False so 1 or 0. lst = [‘hey’,’what’,0,False,None,14] print(sum(x is not None for x in lst)) Or using filter with python2: print(len(filter(lambda x: x is not None, lst))) # py3 -> tuple(filter(lambda x: x is not None, lst)) With python3 … Read more
You can do the following, using itertools.chain: >>> from itertools import chain # timeit: ~3.40 >>> [dict(chain(*map(dict.items, d.values()))) for d in data] [{‘l’: ‘Apple’, ‘b’: ‘Milk’, ‘d’: ‘Meatball’, ‘favourite’: ‘coke’, ‘dislike’: ‘juice’}, {‘l’: ‘Apple1’, ‘b’: ‘Milk1’, ‘dislike’: ‘juice3’, ‘favourite’: ‘coke2’, ‘d’: ‘Meatball2’}] The usage of chain, map, * make this expression a shorthand for the … Read more