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In Python, how to remove items in a list based on the specific string format?

I have a Python list as below:
merged_cells_lst = [
'P19:Q19
'P20:Q20
'P21:Q21
'P22:Q22
'P23:Q23
'P14:Q14
'P15:Q15
'P16:Q16
'P17:Q17
'P18:Q18
'AU9:AV9
'P10:Q10
'P11:Q11
'P12:Q12
'P13:Q13
'A6:P6
'A7:P7
'D9:AJ9
'AK9:AQ9
'AR9:AT9'
'A1:P1'
]
I only want to unmerge the cells in the P and Q columns. Therefore, I seek to remove any strings/items in the merged_cells_lst that does not have the format "P##:Q##".
I think that regex is the best and most simple way to go about this. So far I have the following:
for item in merge_cell_lst:
if re.match(r'P*:Q*'):
pass
else:
merged_cell_lst.pop(item)
print(merge_cell_lst)
The code however is not working. I could use any additional tips/help. Thank you!

Modifying a list while looping over it causes troubles. You can use list comprehension instead to create a new list.
Also, you need a different regex expression. The current pattern P*:Q* matches PP:QQQ, :Q, or even :, but not P19:Q19.
import re
merged_cells_lst = ['P19:Q19', 'P20:Q20', 'P21:Q21', 'P22:Q22', 'P23:Q23', 'P14:Q14', 'P15:Q15', 'P16:Q16', 'P17:Q17', 'P18:Q18', 'AU9:AV9', 'P10:Q10', 'P11:Q11', 'P12:Q12', 'P13:Q13', 'A6:P6', 'A7:P7', 'D9:AJ9', 'AK9:AQ9', 'AR9:AT9', 'A1:P1']
p = re.compile(r"P\d+:Q\d+")
output = [x for x in merged_cells_lst if p.match(x)]
print(output)
# ['P19:Q19', 'P20:Q20', 'P21:Q21', 'P22:Q22', 'P23:Q23', 'P14:Q14', 'P15:Q15',
# 'P16:Q16', 'P17:Q17', 'P18:Q18', 'P10:Q10', 'P11:Q11', 'P12:Q12', 'P13:Q13']

Your list has some typos, should look something like this:
merged_cells_lst = [
'P19:Q19',
'P20:Q20',
'P21:Q21', ...]
Then something as simple as:
x = [k for k in merged_cells_lst if k[0] == 'P']
would work. This is assuming that you know a priori that the pattern you want to remove follows the Pxx:Qxx format. If you want a dynamic solution then you can replace the condition in the list comprehension with a regex match.

comparing two list with different format

I have two list :-
influx = [u'mphhos-fnwp-010101-2',
u'mphhos-fnwp-010101-1',
u'mphhos-fnwp-010101-7',
u'mphhos-fnwp-010101-10',
u'mphhos-fnwp-010101-9',
u'mphhos-fnwp-010101-4',
u'mphhos-fnwp-010101-3',
u'mphhos-fnwp-010101-8',
u'mphhos-fnwp-010101-6',
u'mphhos-fnwp-010101-5',
u'mphhos-fnwp-010101-11']
etcd =[u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-4',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-9',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-1',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-10',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-3',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-6',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-7',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-8',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-11',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-2',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-5']
Etcd is the parent list and I want to compare influx with Etcd.
1.) I want to get all elements which are not present in the list influx and return them.
2.) How I can convert the etcd list into influx list formatting by omitting /xymon/fnwp/mphhos/
Either of the above question will get me my solution.
I tried lots of methods but I am not getting my solution as they are in different format.
I will get my answer by doing set(etcd)-set(influx) but as they are in different format I am getting all the items in the list.

str.rsplit
[x for x in etcd if x.rsplit('/', 1)[1] not in influx]
Per rafaelc's suggestion
infx = set(influx)
[x for x in etcd if x.rsplit('/', 1)[1] not in infx]

One simple solution would be to remove the prefixes
for i, char in enumerate(etcd):
char = char.replace('/xymon/fnwp/mphhos/', '')
etcd[i] = char
And then you could find the differences using set().

influx = [u'mphhos-fnwp-010101-2',
u'mphhos-fnwp-010101-1',
u'mphhos-fnwp-010101-7',
u'mphhos-fnwp-010101-10',
u'mphhos-fnwp-010101-9',
u'mphhos-fnwp-010101-4',
u'mphhos-fnwp-010101-3',
u'mphhos-fnwp-010101-8',
u'mphhos-fnwp-010101-6',
u'mphhos-fnwp-010101-5',
u'mphhos-fnwp-010101-11']
etcd =[u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-4',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-9',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-1',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-10',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-3',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-6',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-7',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-8',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-11',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-2',
u'/xymon/fnwp/mphhos/mphhos-fnwp-010101-5']
etcd = [x.replace('/xymon/fnwp/mphhos/', '') for x in etcd]
# or using regex
# etcd = [re.sub('/xymon/fnwp/mphhos/', '', x) for x in etcd]
diff = set(etcd) - set(influx)
print(diff)

How do I turn each element in a list into a string with quotes

I am using PyCharm IDE.
I frequently work with large data sets, and sometimes I have to iterate through each data.
For instance, I have a list
ticker_symbols = [500.SI, 502.SI, 504.SI, 505.SI, 508.SI, 510.SI, 519.SI...]
How do I automatically format each element into a string with quotes, i .e.
ticker_symbols = ['500.SI', '502.SI', '504.SI', '505.SI', '508.SI', '510.SI', '519.SI'...] ?
Is there a short-cut on PyCharm?

You can just do something like:
ticker_symbols = '[500.SI,502.SI,504.SI,505.SI,508.SI,510.SI,519.SI]'
print(ticker_symbols[1:-1].split(','))
Or like your string:
ticker_symbols = '[500.SI, 502.SI, 504.SI, 505.SI, 508.SI, 510.SI, 519.SI]'
print(ticker_symbols[1:-1].split(', '))
Both reproduce:
['500.SI', '502.SI', '504.SI', '505.SI', '508.SI', '510.SI', '519.SI']

You can use list comprehension:
temp_list = ["'{}'".format(x) for x in ticker_symbols]
Result in:
['500.SI', '502.SI', '504.SI',...]

This will convert your list elements to stringsticker_symbols=str(ticker_symbols[1:-1].split(', '))

limit a float list into 10 digits

I have a list import from a data file.
lines=['1628.246', '100.0000', '0.4563232E-01', '0.4898217E-01', '0.3017656E-02', '0.2271272', '0.2437533', '0.1500232E-01', '0.4102987', '0.4117742', '0.5461504E-02', '2.080838', '0.5527303E-03', '-0.4542367E-03', '-0.2238781E-01', '-0.8196812E-03', '-0.3796306E-01', '-0.7906407E-03', '-0.6738000E-03', '0.000000']
I want to generate a new list include all element in same 10 digits and put back to file
Here is I did:
newline=map(float,lines)
newline=map("{:.10f}".format,newline)
newline=map(str,newline)
jitterfile.write(join(newline)+'\n')
It works, but looks not beautiful. Any idea to make it good looking?

You can do it in a single line like so:
newline=["{:.10f}".format(float(i)) for i in lines]
jitterfile.write(join(newline)+'\n')
Of note, your third instruction newline=map(str,newline) is redundant as the entries in the list are already strings, so casting them is unnecessary.

The map function also accept lambda , also as the result of format is string you don't need to apply the str on your list ,and you need to use join with a delimiter like ',':
>>> newline=map(lambda x:"{:.10f}".format(float(x)),newline)
>>> newline
['1628.2460000000', '100.0000000000', '0.0456323200', '0.0489821700', '0.0030176560', '0.2271272000', '0.2437533000', '0.0150023200', '0.4102987000', '0.4117742000', '0.0054615040', '2.0808380000', '0.0005527303', '-0.0004542367', '-0.0223878100', '-0.0008196812', '-0.0379630600', '-0.0007906407', '-0.0006738000', '0.0000000000']
jitterfile.write(','.join(newline)+'\n')

convert unicode into list

What I have when I convert an png image into blocks then add the section sign (§), I then convert it to a string using:
lframe = [e.encode('utf-8') for e in frame.split(',')]
but when I do, it gives me a:
['\xc2\xa70\xe2\x96\x88\xe2\x96\x88\xe2\x96\x88\xe2\x96\x88\xe2\x96\x88\xe2\x96\
x88\xe2\x96\x88\xc2\xa76\xe2\x96\x88\xe2\x96\x88\xc2\xa70\xe2\x96\x88\xe2\x96\x8
8\xe2\x96\x88\xe2\x96\x88\xe2\x96\x88\xe2\x96\x88\xe2\x96\x88\xc2\xa7r']
What I want to do, is to find a way to convert my output into something like
['\xc2','\xa70','\xe2','\x96','\x88'...]
Thanks!

The code below should do what you want.
lframe = [x for x in [e.encode('utf-8') for e in frame.split(',')][0]]