This question already has answers here:
What does "list comprehension" and similar mean? How does it work and how can I use it?
(5 answers)
Closed 2 years ago.
Can someone help me rewrite this single line loop to a multiple lines for loop in python?
I am trying to understand how it is formatted.
y = {element: r for element in variables(e)}
The dictionary comprehension is equivalent to this loop:
y = {}
for element in variables(e):
y[element] = r
This is called a dict comprehension in python.
This syntax builds a dictionary by taking each element in the list variables(e) and associating it with the value r.
Related
This question already has answers here:
What does "list comprehension" and similar mean? How does it work and how can I use it?
(5 answers)
Closed 12 months ago.
Does anyone know how I can turn the following list comprehension into two nested for loops? When I try and do it I get errors.
data_list = [self.y[a][b] for a in range(side_1, side_2) for b in range(corner_1, corner_2)]
data_list = []
for a in range(side_1, side_2):
for b in range(corner_1, corner_2):
data_list.append(self.y[a][b])
If you need to iterate over every row / column index pair, you should use itertools.product() as a more concise solution than a nested for loop:
from itertools import product
result = []
for a, b in product(range(side_1, side_2), range(corner_1, corner_2)):
result.append(self.y[a][b])
This question already has answers here:
Apply function to each element of a list
(4 answers)
Python Splitting Array of Strings
(6 answers)
Split each string in list and store in multiple arrays
(4 answers)
Closed 1 year ago.
I have a list
list = ['a:b:c:d', 'e:f:g:h', 'i:j:k:l']
What I'm trying to do is make a list of each of it's elements. Something like this:
listelement[0] = list[0].split(':')
print(listelement[0][1])
output: b
I can't seem to figure out how to create something that works similarly to this.
You can try list comprehension to do what you want.
new_list = [element.split(':') for element in list].
Also I would advise against the use of list as a name, since it's a reserved word.
This question already has answers here:
Find an element in a list of tuples
(10 answers)
How to check if all elements of a list match a condition?
(5 answers)
Closed 5 years ago.
I am new in Python and I was curious if I can do something like this:
Let's say that I have a list of tuples and one variable like this:
list = [(123,"a"),(125,"b")]
variable = (123,"c")
Is it possible to search for the first element of the variable in the list like this?
if variable[0] in list[0]:
This question already has answers here:
Convert all strings in a list to integers
(11 answers)
Closed 6 years ago.
Apologies if this question has already been covered!I am trying to convert each element in this list of listsinto integer format. I have used two for loops to iterate through the list, in the same way we do it "C" There is an error that says " Object is not subscriptable" in Line 3 . Am i missing something obvious?
Here is the code:
l=[['1','2'],['3','4']]
for i in range(len(l)):
for j in range(len[i]):
l[j]=int(l[j])
You can use nested list comprehensions:
outer = [['1','2'],['3','4']]
outer_as_ints = [[int(x) for x in inner] for inner in outer]
This question already has answers here:
What does "list comprehension" and similar mean? How does it work and how can I use it?
(5 answers)
Closed 6 years ago.
I'm new to python and in the process of rewriting an old python script and I came across the following line:
some_list = #some list with data
some_variable = [x[0] for x in some_list]
what's x[0]? I don't see x declared previously, is it being created on this line?
what would the value or some_variable be? a list?
update
by 'x' i'm referring to x[0], not the x in the for loop
In this case some_list is a list of sequences, e.g. Lists, tuples, dicts or strings. In your brackets, called a list comprehension, you iterate through some_list. x is the current element of some_list, from which you take the first element x[0] and put it in the new list.
x is the iterating element in your for-loop