All Questions
4,166
questions
1261
votes
9
answers
1.2m
views
How do I iterate through two lists in parallel?
I have two iterables, and I want to go over them in pairs:
foo = [1, 2, 3]
bar = [4, 5, 6]
for (f, b) in iterate_together(foo, bar):
print("f:", f, " | b:", b)
That should ...
- 125k
315
votes
5
answers
528k
views
How to check if all elements of a list match a condition?
I have a list that contains many sub-lists of 3 elements each, like:
my_list = [["a", "b", 0], ["c", "d", 0], ["e", "f", 0], .....]
The ...
- 28.8k
309
votes
7
answers
659k
views
How do I loop through a list by twos? [duplicate]
I want to loop through a Python list and process 2 list items at a time. Something like this in another language:
for(int i = 0; i < list.length(); i+=2)
{
// do something with list[i] and list[...
- 81.4k
219
votes
6
answers
306k
views
How to loop through all but the last item of a list? [duplicate]
Using a for loop, how can I loop through all except the last item in a list? I would like to loop through a list checking each item against the one following it. Can I do this without using indices?
- 49.1k
176
votes
6
answers
236k
views
How to frame two for loops in list comprehension python
I have two lists as below
tags = [u'man', u'you', u'are', u'awesome']
entries = [[u'man', u'thats'],[ u'right',u'awesome']]
I want to extract entries from entries when they are in tags:
result = []
...
- 26.1k
117
votes
0
answers
7k
views
What do two left angle brackets mean? [duplicate]
I saw a loop which I've never seen before:
for (int i = 0; i < (1 << list.Count); i++)
I can't understand what (1 << list.Count) means, maybe someone could explain me this?
- 1,469
101
votes
12
answers
24k
views
Strange result when removing item from a list while iterating over it in Python
I've got this piece of code:
numbers = list(range(1, 50))
for i in numbers:
if i < 20:
numbers.remove(i)
print(numbers)
But, the result I'm getting is:
[2, 4, 6, 8, 10, 12, 14, 16, ...
- 3,676
60
votes
4
answers
22k
views
What is the meaning of list[:] in this code? [duplicate]
This code is from Python's Documentation. I'm a little confused.
words = ['cat', 'window', 'defenestrate']
for w in words[:]:
if len(w) > 6:
words.insert(0, w)
print(words)
And the ...
- 777
57
votes
1
answer
197k
views
What does the "x for x in" syntax mean? [duplicate]
What actually happens when this code is executed:
text = "word1anotherword23nextone456lastone333"
numbers = [x for x in text if x.isdigit()]
print(numbers)
I understand, that [] makes a list, ....
- 1,086
54
votes
13
answers
345k
views
TypeError: 'list' object cannot be interpreted as an integer
The playSound function is taking a list of integers, and is going to play a sound for every different number. So if one of the numbers in the list is 1, 1 has a designated sound that it will play.
...
- 641
50
votes
5
answers
190k
views
ValueError: max() arg is an empty sequence
I've created a GUI using wxFormBuilder that should allow a user to enter the names of "visitors to a business" into a list and then click one of two buttons to return the most frequent and least ...
- 527
48
votes
8
answers
251k
views
How to iterate through a list of dictionaries
My code is
index = 0
for key in dataList[index]:
print(dataList[index][key])
Seems to work fine for printing the values of dictionary keys for index = 0. However, I can't figure out how to ...
- 511
46
votes
8
answers
15k
views
How do I efficiently find which elements of a list are in another list?
I want to know which elements of list_1 are in list_2. I need the output as an ordered list of booleans. But I want to avoid for loops, because both lists have over 2 million elements.
This is what I ...
- 645
43
votes
4
answers
44k
views
How to create all possible combinations from the elements of a list?
I have the following list:
List(a, b, c, d, e)
How to create all possible combinations from the above list?
I expect something like:
a
ab
abc
- 2,013
40
votes
4
answers
130k
views
python modify item in list, save back in list
I have a hunch that I need to access an item in a list (of strings), modify that item (as a string), and put it back in the list in the same index
I'm having difficulty getting an item back into the ...
- 43.4k
29
votes
7
answers
99k
views
How to get the previous element when using a for loop? [duplicate]
Possible Duplicates:
Python - Previous and next values inside a loop
python for loop, how to find next value(object)?
I've got a list that contains a lot of elements, I iterate over the list ...
- 50k
29
votes
4
answers
205k
views
Creating for loop until list.length
I'm reading about for loops right now, and I am curious if it's possible to do a for loop in Python like in Java.
Is it even possible to do something like
for (int i = 1; i < list.length; i++)
...
- 331
28
votes
3
answers
41k
views
For-in loop requires '[UserVehicles]?' to conform to 'Sequence'; did you mean to unwrap optional? Swift
I have a data model which I made for API returns, it is something like this:
struct VehicleData: Codable {
let _embedded: Embedded
}
struct Embedded: Codable {
let userVehicles: [...
- 661
26
votes
5
answers
32k
views
Converting a list of data frames into individual data frames in R [duplicate]
I have been searching high and low for what I think is an easy solution.
I have a large data frame that I split by factors.
eqRegions <- split(eqDataAll, eqDataAll$SeismicRegion)
This now ...
- 1,790
26
votes
4
answers
19k
views
Java synchronized list for loop
Documentation on synchronizedList states that,
It is imperative that the user manually synchronize on the returned list when iterating over it:
List list = Collections.synchronizedList(new ArrayList(...
- 271
25
votes
4
answers
183k
views
python - if not in list [duplicate]
I have two lists:
mylist = ['total','age','gender','region','sex']
checklist = ['total','civic']
I have to work with some code I have inherited which looks like this:
for item in mylist:
if ...
- 13.7k
24
votes
1
answer
125k
views
Break for loop in an if statement [duplicate]
Currently having trouble with breaking this for loop. I want to break it if the variable is not found in this list so it can move two another for loop. It expects an indented block for the top of the ...
- 269
22
votes
4
answers
51k
views
Using forloop.counter value as list index in a Django template
in my Django 1.1.1 application I've got a function in the view that returns to his template a range of numbers and a list of lists of items, for example:
...
data=[[item1 , item2, item3], [item4, ...
- 255
20
votes
3
answers
48k
views
Adding data frames as list elements (using for loop)
I have in my environment a series of data frames called EOG. There is one for each year between 2006 and 2012. Like, EOG2006, EOG2007...EOG2012. I would like to add them as elements of a list.
First,...
- 753
19
votes
6
answers
13k
views
How can I use a list comprehension to extend a list in python? [duplicate]
I'm not experienced in Python, and I often write code that (simplified) looks like this:
accumulationList = []
for x in originalList:
y = doSomething(x)
accumulationList.append(y)
return ...
- 58.5k
18
votes
3
answers
42k
views
selenium.common.exceptions.InvalidArgumentException: Message: invalid argument error invoking get() with urls read from text file with Selenium Python
I have a list of URLs in a .txt file that I would like to run using selenium.
Lets say that the file name is b.txt in it contains 2 urls (precisely formatted as below):
https://www.google.com/,https:...
- 183
17
votes
5
answers
10k
views
List comprehension iterating over two lists is not working as expected [duplicate]
I want to iterate over two lists. The first list contains some browser user-agents and the second list contains versions of those browsers. I want to filter out only those user-agents whose version is ...
- 1,046
16
votes
1
answer
58k
views
Adding elements to a list in for loop in R
I'm trying to add elements to a list in a for loop. How can I set the field name?
L <- list()
for(i in 1:N)
{
# Create object Ps...
string <- paste("element", ...
- 1,608
15
votes
4
answers
877
views
write better code instead of 2 for loops
I have 2 for loops and I want to make it better like list comprehension or lambda or else.
how can i achieve the same?
for example :
filename = ['a.txt', 'b.txt', 'c.txt']
for files in filename:
...
- 19k
15
votes
4
answers
64k
views
How to convert a for loop output to a list?
For example:
for y,x in zip(range(0,4,1),range(0,8,2)):
print(x+y)
Returns:
0
3
6
9
What I want is:
['0', '3', '6', '9']
How can I achieve this?
- 235
15
votes
3
answers
15k
views
How to iterate in a cartesian product of lists
I would like to iterate in a for loop using 3 (or any number of) lists with any number of elements, for example:
from itertools import izip
for x in izip(["AAA", "BBB", "CCC"], ["M", "Q", "S", "K", "...
- 28.8k
15
votes
2
answers
11k
views
Python - Any way to avoid several if-statements inside each other in a for-loop?
I need a better way to do this. I'm new with programming but I know that this is a very inefficient way of doing it and that I need a function for this, I just don't know how to do it exactly. any ...
- 171
14
votes
6
answers
23k
views
Why does a for-loop with pop-method (or del statement) not iterate over all list elements [duplicate]
I am new to Python and experimenting with lists
I am using Python 3.2.3 (default, Oct 19 2012, 20:13:42), [GCC 4.6.3] on linux2
Here is my samplecode
>>> l=[1,2,3,4,5,6]
>>> for i ...
- 151
12
votes
2
answers
22k
views
l.append[i], object is not subscriptable? [closed]
When I do:
l = []
for i in range(10):
if i%3 == 0 or i%5 == 0:
l.append[i]
print sum(l)
I get
Traceback (most recent call last):
File "PE1.py", line 4, in <module>
l.append[...
- 10.8k
12
votes
1
answer
3k
views
How to iterate over list of Dates without coercion to numeric?
This is related to Looping over a Date or POSIXct object results in a numeric iterator
> dates <- as.Date(c("2013-01-01", "2013-01-02"))
> class(dates)
[1] "Date"...
- 7,286
11
votes
5
answers
112k
views
How to create and fill a list of lists in a for loop
I'm trying to populate a list with a for loop. This is what I have so far:
newlist = []
for x in range(10):
for y in range(10):
newlist.append(y)
and at this point I am stumped. I was ...
- 113
11
votes
4
answers
27k
views
Populate a list in Kotlin with a for loop
It's been a while that I just started to learn how to develop in Kotlin.
There is this thing that I am working on, I am trying to parse a list into another type of list. Basically they are the same ...
- 263
11
votes
3
answers
45k
views
create lists of unique names in a for -loop in python
I want to create a series of lists with unique names inside a for-loop and use the index to create the liste names. Here is what I want to do
x = [100,2,300,4,75]
for i in x:
list_i=[]
I want to ...
- 30.7k
10
votes
4
answers
37k
views
How to change variables fed into a for loop in list form
I am writing a basic program in Python that prompts the user to enter 5 test scores. The program will then convert each test score to a grade point (i.e. 4.0, 3.0, 2.0...), and then afterwards take ...
- 195
10
votes
3
answers
4k
views
python: using list slice as target of a for loop
I found this code snippet to be very interesting.
a = [0, 1, 2, 3]
for a[-1] in a:
print(a)
Output is as follows:
[0, 1, 2, 0]
[0, 1, 2, 1]
[0, 1, 2, 2]
[0, 1, 2, 2]
I am trying to understand ...
- 115
9
votes
3
answers
3k
views
Find first item with alphabetical precedence in list with numbers
Say I have a list object occupied with both numbers and strings. If I want to retrieve the first string item with the highest alphabetical precedence, how would I do so?
Here is an example attempt ...
- 101
9
votes
5
answers
21k
views
Loop print through two lists to get two columns with fixed(custom set) space between the first letter of each element of each list
Suppose I have these two lists:
column1 = ["soft","pregnant","tall"]
column2 = ["skin","woman", "man"]
How do I loop print through these two lists while using a custom, fixed space(say 10, as in ...
- 10.8k
9
votes
4
answers
33k
views
Change values in a list using a for loop (python)
I currently have some code that reads like this:
letters = {
10 : "A",
11 : "B",
12 : "C",
13 : "D",
14 : "E",
15 : "F"
}
vallist = [rd1, rd2, gd1, gd2, bd1, bd2]
for i in vallist:
if i >= 10:
...
- 310
9
votes
6
answers
2k
views
Cycling values of a list [duplicate]
I'm new to coding and am trying to write a simple code that will take a list, say [1,2,3] and cycle the elements n number of times. So if n=1, I should get A=[3,1,2]. If n=2, I should get A=[2,3,1]....
- 347
9
votes
1
answer
2k
views
Nested List comprehension in Python
I have a List inside of a List in Python and i want to convert them into a single list using List comprehension:
>>> aa = [[1,2],[1,2]]
>>> bb = [num for num in numbers for numbers ...
- 1,356
8
votes
5
answers
11k
views
R remove objects from a list with if else statement
I have a list of data frames, and would like to remove those with less than 2 rows off from mylist:
a<-data.frame(x=c(1:4),y=c("m", "n", "o", "p"))
b<-data.frame(x=c(2:6),y=c("q", "w", "e", "r",...
- 303
8
votes
3
answers
2k
views
In Python, are conditions in a loop re-evaluated before a new iteration is executed?
As with regards to python, when it comes to a for loop, will it re-evaluate the upper bound before re-iteration?
Say I have the following scenario:
def remove(self,list,element):
for x in range(...
- 174
8
votes
1
answer
10k
views
Populating a list with lm objects
I am trying to populate a named list with the results of an OLS in R. I tried
li = list()
for (i in 1:10)
li[["RunOne"]][i] = lm(y~x)
Here RunOne is a random name that designates the fitting run ...
- 1,872
8
votes
1
answer
14k
views
Naming list items via loop in R
I want to take a list, create a String vector of the names of the list items, filling in blanks with a generic name and then set the names vector as the names of the list.
My code works fine for ...
- 461
8
votes
2
answers
3k
views
Adjust all nested lists to the same length
I am referring to this this specific answer Making nested lists same length. Since I don't have the permissions to comment yet and answering with a question to that topic would violate the rules, I am ...
- 151