Develop Reference

Unable to store values in an array from for loop in python

First I tried directly storing values from a list having the name 'data' in an array variable 'c' using loop but 'none' got printed
for i in data:
print(i['name'])
c=i['name']
Here print(i['name']) perfectly worked and output appeared
This is the working ouput
Then I printed c in order to print the values generated using loop. The ouput came as none.
print(c)
Then I tried another way by storing the values and making the array iterable at the same time using for loop. An error occurred which I was unable to resolve.
for i in data:
b[c]=i['name']
c=c+1
The error apeared is as follow-
I have tried two ways, if there is any other way please help me out as I am new to python.

It looks like the variable 'data' is a dictionary.
If you want to add each name from that dictionary to a list:
# create a new list variable
names = []
for i in data:
name = i['name']
print(name)
# add the name to the list
names.append(name)
# output the new list
print(names)

Assuming your data object here is a list like [{"name": "Mr. Green", ...}, {"name": "Mr. Blue", ...}].
If your goal is to end up with c == ["Mr. Green", "Mr. Blue"], then you're looking for something like:
c = []
for i in data:
c.append(i['name'])
print(c)
or you can accomplish tasks like these using list comprehensions like:
c = [i['name'] for i in data]
print(c)
The first code example you posted is iterating through the items in data and reassigning the value of c to each item's name key - not adding them to a list("array"). Without knowing more about the code you ran to produce the screenshot and/or the contents of data, it's hard to say why you're seeing print(c) produce None. I'd guess the last item in data is something like {"name": None, ...} which if it's coming from JSON is possible if the value is null. Small note: I'd generally use .get("name") here instead so that your program doesn't blow up if an item is missing a "name" key entirely.
For your second code example, the error is different but I think falls along a similar logical fallacy which is that lists in python function differently from primitives(things like numbers and strings). For the interpreter to know that b or c are supposed to be lists("arrays"), they need to be instantiated differently and they have their own set of syntax/methods for mutation. For example, like arrays in other languages, lists are indexed by position so doing b[c] = <something> will only work if c is an integer. So something similar to your second example that would also produce a list of names like my above would be:
b = [None] * len(data)
c = 0
for i in data:
b[c]=i['name']
c=c+1
Note that if you only initialize b = [], you get an IndexError: list assignment index out of range on the initial assignment of b[0] = "some name" because the list is of size 0.

Add
b = []
above your first line of code. As the error is saying that you have not (and correctly so) defined the list to append.
I personally would use list comprehension here
b = [obj['name'] for obj in data]
where obj is i as you have defined it.

Python: Index slicing from a list for each index in for loop

I got stuck in slicing from a list of data inside a for loop.
list = ['[init.svc.logd]: [running]', '[init.svc.logd-reinit]: [stopped]']
what I am looking for is to print only key without it values (running/stopped)
Overall code,
for each in list:
print(each[:]) #not really sure what may work here
result expected:
init.svc.logd
anyone for a quick solution?

If you want print only the key, you could use the split function to take whatever is before : and then replace [ and ] with nothing if you don't want them:
list = ['[init.svc.logd]: [running]', '[init.svc.logd-reinit]: [stopped]']
for each in list:
print(each.split(":")[0].replace('[','').replace(']','')) #not really sure what may work here
which gives :
init.svc.logd
init.svc.logd-reinit

You should probably be using a regular expression. The concept of 'key' in the question is ambiguous as there are no data constructs shown that have keys - it's merely a list of strings. So...
import re
list_ = ['[init.svc.logd]: [running]', '[init.svc.logd-reinit]: [stopped]']
for e in list_:
if r := re.findall('\[(.*?)\]', e):
print(r[0])
Output:
init.svc.logd
init.svc.logd-reinit
Note:
This is more robust than string splitting solutions for cases where data are unexpectedly malformed

Access an element in a list of lists in python

I am new to python and am trying to access a single specific element in a list of lists.
I have tried:
line_list[2][0]
this one isn't right as its a tuple and the list only accepts integers.
line_list[(2, 0)]
line_list[2, 0]
This is probably really obvious but I just can't see it.
def rpd_truncate(map_ref):
#Munipulate string in order to get the reference value
with open (map_ref, "r") as reference:
line_list = []
for line in reference:
word_list = []
word_list.append(line[:-1].split("\t\t"))
line_list.append(word_list)
print line_list[2][0]
I get the exact same as if I used line_list[2]:
['Page_0', '0x00000000', '0x002DF8CD']

actually split will return a list
more over you don't require word_list variable
for line in reference:
line_list.append(line[:-1].split("\t\t"))
print line_list[2][0]

How do I pull certain values from a list of lists in python?

def get_monthly_averages(original_list):
#print(original_list)
daily_averages_list = [ ]
for i in range (0, len(original_list)):
month_list = i[0][0:7]
volume_str = i[5]
#print(volume_str)
adj_close_str = i[6]
#print(adj_close_str)
daily_averages_tuple = (month_list,volume_str,adj_close_str)
daily_averages_list.append(daily_averages_tuple.split(','))
return daily_averages_list
I have a list like
[
['2004-08-30', '105.28', '105.49', '102.01', '102.01', '2601000', '102.01'],
['2004-08-27', '108.10', '108.62', '105.69', '106.15', '3109000', '106.15'],
['2004-08-26', '104.95', '107.95', '104.66', '107.91', '3551000', '107.91'],
['2004-08-25', '104.96', '108.00', '103.88', '106.00', '4598900', '106.00'],
['2004-08-24', '111.24', '111.60', '103.57', '104.87', '7631300', '104.87'],
['2004-08-23', '110.75', '113.48', '109.05', '109.40', '9137200', '109.40'],
['2004-08-20', '101.01', '109.08', '100.50', '108.31', '11428600', '108.31'],
['2004-08-19', '100.00', '104.06', '95.96', '100.34', '22351900', '100.34']
]
I am attempting to pull certain multiple values from within each list within the 'long' list. I need to use beginning python techniques. For instance, we haven't learned lambda in the class as of yet. MUST use beginning techniques.
as of right now the lines using i[][] are giving me a type error saying that 'int' is not subscriptable.

Your variable i is an integer. You should be indexing into original_list and not i.

I think you wwant
month_list = original_list[i][0][0:7]
volume_str = original_list[i][5]
#print(volume_str)
adj_close_str = original_list[i][6]

Don't use range to iterate over lists. Do this:
for datestr, n1, n2, n3, someval, otherval in original_list:
#do your stuff here
This will iterate over every list in original_list, and assign the 6 elements of each such list to the variables given.

use slice in for loop to build a list

I would like to build up a list using a for loop and am trying to use a slice notation. My desired output would be a list with the structure:
known_result[i] = (record.query_id, (align.title, align.title,align.title....))
However I am having trouble getting the slice operator to work:
knowns = "output.xml"
i=0
for record in NCBIXML.parse(open(knowns)):
known_results[i] = record.query_id
known_results[i][1] = (align.title for align in record.alignment)
i+=1
which results in:
list assignment index out of range.
I am iterating through a series of sequences using BioPython's NCBIXML module but the problem is adding to the list. Does anyone have an idea on how to build up the desired list either by changing the use of the slice or through another method?
thanks zach cp
(crossposted at [Biostar])1

You cannot assign a value to a list at an index that doesn't exist. The way to add an element (at the end of the list, which is the common use case) is to use the .append method of the list.
In your case, the lines
known_results[i] = record.query_id
known_results[i][1] = (align.title for align in record.alignment)
Should probably be changed to
element=(record.query_id, tuple(align.title for align in record.alignment))
known_results.append(element)
Warning: The code above is untested, so might contain bugs. But the idea behind it should work.

Use:
for record in NCBIXML.parse(open(knowns)):
known_results[i] = (record.query_id, None)
known_results[i][1] = (align.title for align in record.alignment)
i+=1

If i get you right you want to assign every record.query_id one or more matching align.title. So i guess your query_ids are unique and those unique ids are related to some titles. If so, i would suggest a dictionary instead of a list.
A dictionary consists of a key (e.g. record.quer_id) and value(s) (e.g. a list of align.title)
catalog = {}
for record in NCBIXML.parse(open(knowns)):
catalog[record.query_id] = [align.title for align in record.alignment]
To access this catalog you could either iterate through:
for query_id in catalog:
print catalog[query_id] # returns the title-list for the actual key
or you could access them directly if you know what your looking for.
query_id = XYZ_Whatever
print catalog[query_id]