Unpacking generalizations Question: PEP 448 — Additional Unpacking Generalizations allowed: >>> LOL = [[1, 2], [‘three’]] >>> [*LOL[0], *LOL[1]] [1, 2, ‘three’] Alright! Goodbye itertools.chain. Never liked you much anyway. >>> [*L for L in LOL] File "<ipython-input-21-e86d2c09c33f>", line 1 [*L for L in LOL] ^ SyntaxError: iterable unpacking cannot be used in comprehension Oh. …
Unpacking tuples in a python list comprehension (cannot use the *-operator) Question: I am trying to create a list based on another list, with the same values repeated 3 times consecutively. At the moment, I am using: >>> my_list = [ 1, 2 ] >>> three_times = [] >>> for i in range( len( my_list …
Python: Splat/unpack operator * in python cannot be used in an expression? Question: Does anybody know the reasoning as to why the unary (*) operator cannot be used in an expression involving iterators/lists/tuples? Why is it only limited to function unpacking? or am I wrong in thinking that? For example: >>> [1,2,3, *[4,5,6]] File “<stdin>”, …
Getting only element from a single-element list in Python? Question: When a Python list is known to always contain a single item, is there a way to access it other than: mylist[0] You may ask, ‘Why would you want to?’. Curiosity alone. There seems to be an alternative way to do everything in Python. Asked …
Why is it valid to assign to an empty list but not to an empty tuple? Question: This came up in a recent PyCon talk. The statement [] = [] does nothing meaningful, but it does not throw an exception either. I have the feeling this must be due to unpacking rules. You can do …
pandas apply function that returns multiple values to rows in pandas dataframe Question: I have a dataframe with a timeindex and 3 columns containing the coordinates of a 3D vector: x y z ts 2014-05-15 10:38 0.120117 0.987305 0.116211 2014-05-15 10:39 0.117188 0.984375 0.122070 2014-05-15 10:40 0.119141 0.987305 0.119141 2014-05-15 10:41 0.116211 0.984375 0.120117 2014-05-15 …
Why can a dictionary be unpacked as a tuple? Question: Today, I saw one statement which didn’t throw an exception. Can anyone explain the theory behind it? >>> x, y = {‘a’: 2, ‘b’: 5} >>> x ‘a’ >>> y ‘b’ Asked By: nik_kgp || Source Answers: In Python, every iterable can be unpacked1: >>> …
What does *tuple and **dict mean in Python? Question: As mentioned in PythonCookbook, * can be added before a tuple. What does * mean here? Chapter 1.18. Mapping Names to Sequence Elements: from collections import namedtuple Stock = namedtuple(‘Stock’, [‘name’, ‘shares’, ‘price’]) s = Stock(*rec) # here rec is an ordinary tuple, for example: rec …
Split list into different variables Question: I have a list like this: [(‘love’, ‘yes’, ‘no’), (‘valentine’, ‘no’, ‘yes’), (‘day’, ‘yes’,’yes’)] How do I split this list into three variables where each variable holds one tuple, i.e. var1 = (‘love’, ‘yes’, ‘no’) var2 = (‘valentine’, ‘no’, ‘yes’) var3 = (‘day’, ‘yes’,’yes’) Asked By: Eagle || Source …
How does swapping of members in tuples (a,b)=(b,a) work internally? Question: In [55]: a = 5 In [56]: b = 6 In [57]: (a, b) = (b, a) In [58]: a Out[58]: 6 In [59]: b Out[59]: 5 How does this swapping of values of a and b work internally? Its definitely not using a …
