The original list project_keys = sorted(projects.keys()) is [101, 102, 103, 104, 105, 106, 107, 108, 109, 110] where the following projects were deemed invalid this year: 108, 109, 110. Thus: for project in projects.itervalues(): # The projects dictionary is mapped to the Project class if project.invalid: # Where invalid is a...
Here is the code I was trying to turn into a list comprehension: table = '' for index in xrange(256): if index in ords_to_keep: table += chr(index) else: table += replace_with Is there a way to add the else statement to this comprehension? table = ''.join(chr(index) for index in xrange(15) if index in ords_to_...
In a Python program I'm writing I've compared using a for loop and increment variables versus list comprehension with map(itemgetter) and len() when counting entries in dictionaries which are in a list. It takes the same time using a each method. Am I doing something wrong or is there a better approach? Here is a greatly simplified and ...
I have a set of lists that look like this: conditions = [ ["condition1", ["sample1", "sample2", "sample3"]], ["condition2", ["sample4", "sample5", "sample6"], ...] how can I do the following things efficiently and elegantly in Python? Find all the elements in a certain condition? e.g. get all the samples in condition2. Right now I...
Given two vectors X and Y, I have to find their correlation, i.e. their linear dependence/independence. Both vectors have equal dimension. The result should be a floating point number from [-1.0 .. 1.0]. Example: X=[-1, 2, 0] Y=[ 4, 2, -0.3] Find y = cor(X,Y) such that y belongs to [-1.0 .. 1.0]. It should be a simple construct...
I'm parsing a string that doesn't have a delimiter but does have specific indexes where fields start and stop. Here's my list comprehension to generate a list from the string: field_breaks = [(0,2), (2,10), (10,13), (13, 21), (21, 32), (32, 43), (43, 51), (51, 54), (54, 55), (55, 57), (57, 61), (61, 63), (63, 113), (113, 163), (163, 213...
I have a dictionary, with 300 key value pairs, where each of the keys are integers and the values are dictionaries with three key value pairs. The inner dictionaries all have the same keys, but different values. The whole thing looks pretty much like this: nested_dicts = {1: {'name1':88.4, 'name2':22.1, 'name3':115.7}, 2: {'...
given: template = {'a': 'b', 'c': 'd'} add = ['e', 'f'] k = 'z' I want to use list comprehension to generate [{'a': 'b', 'c': 'd', 'z': 'e'}, {'a': 'b', 'c': 'd', 'z': 'f'}] I know I can do this: out = [] for v in add: t = template.copy() t[k] = v out.append(t) but it is a little verbose and has no advantage over what I'm...
I have a tuple of tuples - for example: tupleOfTuples = ((1, 2), (3, 4), (5,)) I want to convert this into a flat, one-dimensional list of all the elements in order: [1, 2, 3, 4, 5] I've been trying to accomplish this with list comprehension. But I can't seem to figure it out. I was able to accomplish it with a for-each loop: myLi...
I just learned about list comprehension, which is a great fast way to get data in a single line of code. But something's bugging me. In my test I have this kind of dictionaries inside the list: [{'y': 72, 'x': 94, 'fname': 'test1420'}, {'y': 72, 'x': 94, 'fname': 'test277'}] The list comprehension s = [ r for r in list if r['x'] > 92...
Here is a code snippet that shows the code I would like to optimize: result = [(item, foo(item)) for item in item_list if cond1(item) and cond2(foo(item))] In the above snippet I call foo(item) twice. I can't think of a way to iterate over the list only once maintain both item and foo(item) for the conditional and ...
I'm trying to learn Scala and tried to write a sequence comprehension that extracts unigrams, bigrams and trigrams from a sequence. E.g., [1,2,3,4] should be transformed to (not Scala syntax) [1; _,1; _,_,1; 2; 1,2; _,1,2; 3; 2,3; 1,2,3; 4; 3,4; 2,3,4] In Scala 2.8, I tried the following: def trigrams(tokens : Seq[T]) = { var t1 : ...
I have a list of strings parsed from somewhere, in the following format: [key1, value1, key2, value2, key3, value3, ...] I'd like to create a dictionary based on this list, like so: {key1:value1, key2:value2, key3:value3, ...} An ordinary for loop with index offsets would probably do the trick, but I wonder if there's a Pythonic wa...
Suppose I have the following object: class Foo(object): def __init__(self, name=None): self.name = name def __repr__(self): return self.name And a list containing multiple instances, such as: list = [Foo(name='alice'), Foo(name='bob'), Foo(name='charlie')] If I want to find an object with a given name, I could use the ...
>>> a=range(5) >>> [a[i] for i in range(0,len(a),2)] ## list comprehension for side effects [0, 2, 4] >>> a [0, 1, 2, 3, 4] >>> [a[i]=3 for i in range(0,len(a),2)] ## try to do assignment SyntaxError: invalid syntax >>> def setitem(listtochange,n,value): ## function to overcome limitation listtochange[n]=value return value >>> ...
I'm looking for a better/more Pythonic solution for the following snippet count = sum(1 for e in iterable if e) ...
Or How to if-statement in a modified list. I've been reading StackOverflow for a while (thanks to everyone). I love it. I also seen that you can post a question and answer it yourself. Sorry if I duplicate, but I didn't found this particular answer on StackOverflow. How do you verify if a element is in a list but modify it in the sa...
I'm reading Simon Thompson's Haskell: The Craft of Functional Programming, and I'm wondering how does this work: perms [] = [[]] perms xs = [ x:ps | x <- xs , ps <- perms ( xs\\[x] ) ] I can't seem to grasp how that perms( xs\\[x] ) is supposed to function. The trace of a two element list shows: perms [2,3] [ x:ps | x <- [2,3] , ps...
I want to get a running total from a list of numbers. For demo purposes, I start with a sequential list of numbers using range a = range(20) runningTotal = [] for n in range(len(a)): new = runningTotal[n-1] + a[n] if n > 0 else a[n] runningTotal.append(new) # This one is a syntax error # runningTotal = [a[n] for n in range(le...
Sorry if the question is bit confusing. This is similar to this question I think this the above question is close to what I want, but in Clojure. There is another question I need something like this but instead of '[br]' in that question, there is a list of strings that need to be searched and removed. Hope I made myself clear. I...