tuples

问题 I would like to automatically create a tuple (to be passed to a scipy.stats function) from columns in a pandas dataframe, so that each row of the tuple are the values from each column of the dataframe. here is the header from my dataframe: 4_3-a-0 5_3-a-4 7_3-a-3 datetime_pac 2015-09-03 22:00:00 -100.4 -96.857143 -55.000000 2015-09-03 22:01:00 -100.5 -91.700000 -55.600000 2015-09-03 22:02:00 -100.4 -90.875000 -55.900000 2015-09-03 22:03:00 -100.4 -94.000000 -55.555556 2015-09-03 22:04:00 -100

问题 Tuple elements may have side-effects, and some of them may depend on others. Consider this program: fn main() { let mut v = vec![1, 2]; match (v.pop(), v.pop()) { (Some(z), Some(y)) => println!("y = {}, z = {}", y, z), _ => unreachable!(), } } Does it output y = 1, z = 2 or y = 2, z = 1 ? A few rounds on the Rust Playground suggests the former on stable 1.32.0, but maybe it would change if I ran it more times, recompiled the compiler, changed compiler versions, etc. Is there a documented

问题 Tuple elements may have side-effects, and some of them may depend on others. Consider this program: fn main() { let mut v = vec![1, 2]; match (v.pop(), v.pop()) { (Some(z), Some(y)) => println!("y = {}, z = {}", y, z), _ => unreachable!(), } } Does it output y = 1, z = 2 or y = 2, z = 1 ? A few rounds on the Rust Playground suggests the former on stable 1.32.0, but maybe it would change if I ran it more times, recompiled the compiler, changed compiler versions, etc. Is there a documented

问题 If I have: my_list = [('foo', 'bar'), ('floo', 'blar')] how can I easily test if some string is in the first element in any of those tuples? something like: if 'foo' in my_list where we are just checking the first element of each tuple in the list? 回答1: If you want to check only against the first item in each tuple: if 'foo' in (item[0] for item in my_list) Alternatively: if any('foo' == item[0] for item in my_list) 回答2: You can first extract a list of only the first items and then perform a

问题 I've got a list of tuples extracted from a table in a DB which looks like ( key , foreignkey , value ). There is a many to one relationship between the key and foreignkeys and I'd like to convert it into a dict indexed by the foreignkey containing the sum of all values with that foreignkey, i.e. { foreignkey , sumof( value ) }. I wrote something that's rather verbose: myDict = {} for item in myTupleList: if item[1] in myDict: myDict [ item[1] ] += item[2] else: myDict [ item[1] ] = item[2]

问题 If I have a tuple such as (1,2,3,4) and I want to assign 1 and 3 to variables a and b I could obviously say myTuple = (1,2,3) a = my_tuple[0] b = myTuple[2] Or something like (a,_,b,_) = myTuple Is there a way I could unpack the values, but ignore one or more of them of them? 回答1: Your solution is fine in my opinion. If you really have a problem with assigning _ then you could define a list of indexes and do: a = (1, 2, 3, 4, 5) idxs = [0, 3, 4] a1, b1, c1 = (a[i] for i in idxs) 回答2: I

问题 I was hoping for an elegant or effective way to multiply sequences of integers (or floats). My first thought was to try (1, 2, 3) * (1, 2, 2) would result (1, 4, 6) , the products of the individual multiplications. Though python isn't preset to do that for sequences. Which is fine, I wouldn't really expect it to. So what's the pythonic way to multiply (or possibly other arithmetic operations as well) each item in two series with and to their respective indices? A second example (0.6, 3.5) *

问题 I was hoping for an elegant or effective way to multiply sequences of integers (or floats). My first thought was to try (1, 2, 3) * (1, 2, 2) would result (1, 4, 6) , the products of the individual multiplications. Though python isn't preset to do that for sequences. Which is fine, I wouldn't really expect it to. So what's the pythonic way to multiply (or possibly other arithmetic operations as well) each item in two series with and to their respective indices? A second example (0.6, 3.5) *

问题 Suppose I want a list of tuples. Here's my first idea: li = [] li.append(3, 'three') Which results in: Traceback (most recent call last): File "./foo.py", line 12, in <module> li.append('three', 3) TypeError: append() takes exactly one argument (2 given) So I resort to: li = [] item = 3, 'three' li.append(item) which works, but seems overly verbose. Is there a better way? 回答1: Add more parentheses: li.append((3, 'three')) Parentheses with a comma create a tuple, unless it's a list of

问题 I am accessing an element of length 2 tuple by tuple_name[0] but the python interpreter keeps giving me error Index out of bounds . Here is the code for reference: def full(mask): v = True for i in mask: if i == 0: v = False return v def increment(mask, l): i = 0 while (i < l) and (mask[i] == 1): mask[i] = 0 i = i+1 if i < l: mask[i] = 1 def subset(X,Y): s = len(X) mask = [0 for i in range(s)] yield [] while not full(mask): increment(mask, s) i = 0 yield ([X[i] for i in range(s) if mask[i]] ,