Develop Reference

Python-string formatting with variable length

I'm trying to pad dynamic elements within a table, but it seems as though the native padding function doesn't work with variables. Just wondering if I'm doing something wrong or if there are simple alternatives to center padding. I know of ljust and rjust but there is no m(iddle)just for some reason.
Simple example:
a=10
b='hi'
print(f'{b:^a}')
or
a=10
b='hi'
print('{:^a}'.format(b))
produces
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: Unknown format code 'a' for object of type 'str'
Typing 10 in place of a in the print statement makes it work as intended, so I'm guessing 'a' is being interpreted as a string by the string formatted. Is a helper function the only way out here?

In [114]: print(f'{b:^{a}}')
hi
In [115]: print(f'"{b:^{a}}"')
" hi "

Probably want to add another set of brackets
a=10
b='hi'
print(f'{b:^{a}}')

Use Python reserved words in an XML File

I'm currently trying to use python's (3.6) xml.etree.ElementTree commands to write an xml file. Some of the Elements and Subelements I need to write must have "id" and "map" fields, which are reserved python words.
My problem is contained in the following line of code:
ET.SubElement(messages,'trigger',thing='1',bob='a', max='5')
But "max" is a function and I can't use it. Is there a character I can place there to allow me to write this field as I desire? Or some sort of known workaround?
EDIT: I am aware that an '_' stops the python from processing the word, but unfortunately this underscore will show up in my file...so I am trying to see if there is an 'invisible' option for the file I will later be writing.
Thanks much!

Python functions are no problem in the left side of a keyword expression:
>>> def abc(**kwargs):
print kwargs
>>> abc(id=2)
{'id': 2}
>>>
id, map, int, float, str, repr, etc. are built in symbols, not reserved words. You may use them like any other bunch of letters, but assigning it another value replaces the built in symbol:
>>> int(2.5)
2
>>> int = "5"
>>> int(2.5)
Traceback (most recent call last):
File "<pyshell#10>", line 1, in <module>
int(2.5)
TypeError: 'str' object is not callable
Notice how the first line is entirely legal, but will trigger a warning if you have a good IDE like pycharm.
If you want to send a actual reserved word to a function, like print, None, yield, or try, you can use the double star ** to convert a dictionary into keyword arguments, for example:
>>> abc(**{"print":2, "None":3})
{'print': 2, 'None': 3}
I hope this answers your question!

Arabic regex giving TypeError

I have this simple regex:
text = re.sub("[إأٱآا]", "ا", text)
However, I get this (Python 2.7) error:
TypeError: expected string or buffer
I'm a regex newbie, I imagine this is a simple thing to fix, but I'm
not sure how? Thanks.

Define all your strings as unicode and don't forget to add the encoding line in the header of the file:
#coding: utf-8
import re
text = re.sub(u"[إأٱآا]", u"ا", u"الآلهة")
print text
To get:
الالهة

re.sub expects regex as first parameter. You need to escape the left bracket in your patterns. Use \[ instead of [

Sorry I couldn't fit this in the comments section. There is nothing wrong in the re.sub as far as I understand. Because if you code the chars back to unicode you get the below verbatim.
text = re.sub("[\u0625\u0623\u0671\u0622\u0627]", "\u0627", text)
Because it is arabic, remember it is right to left, the visuals are a bit jumbled that's all.
It is actually trying to replace a set of chars with one char.
Although why would one replace \u0627 with \u0627, I do not know.
The issue I believe is with text. If you can do print(text), then we can see if there are any chars in it that belong to "[إأٱآا]" == "[\u0625\u0623\u0671\u0622\u0627]"
Just a quip the \u0627 is the smallest vertical line on the left ;-)
Little help in understanding what it actually is use(just copy the whole statement in the question and do the below)
for x in mystr: print(x + '-' + str(ord(x)))
http://www.fileformat.info/info/unicode/char/0627/index.htm
EDITED
>>> re.sub(myset,myrep,text)
u'\u0627\u0627\u0627abc'
>>> res=re.sub(myset,myrep,text)
>>> res
u'\u0627\u0627\u0627abc'
>>> myrep
u'\u0627'
>>> myset
u'[\u0625\u0623\u0671\u0622\u0627]'
>>> text
u'\u0625\u0623\u0623abc'
>>> print(res)
اااabc
>>> print(myrep)
ا
>>> print(myset)
[إأٱآا]
>>> print(text)
إأأabc
>>>
So in essence All Works Well and the error is else where.
I think reproduced the error that is occurring elsewhere and here it is
>>> print(u'\u0625'+ord(u'\u0625'))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: coercing to Unicode: need string or buffer, int found
Cheers!

This is how I eventually did it:
sText = re.sub(ur"[\u0625|\u0623|\u0671|\u0622|\u0627]", ur"\u0627", sText)
Thank you all for your help.

Get last character of string using `format`

I have to build a path from a given id using this template :
<last digit of id>/<second last digit of id>/<full id>
For instance, if my id is 3412, the expected result would be :
2/1/3412
The id is supposed to have at least 2 digits.
The first thing I tried was:
>>> "{my_id[3]}/{my_id[2]}/{my_id}".format(my_id=str(3412))
'2/1/3412'
But this would work only if the id is 4 digits long.
So what I was expecting to do then was:
>>> "{my_id[-1]}/{my_id[-2]}/{my_id}".format(my_id=str(3412))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: string indices must be integers
My question here is why can't I use negative indices in my string specifier? And why is Python telling me I'm not using integer indices? I didn't find anything in the documentation about it.
I know there are many other ways to do this, but I'm just curious about why this one does not work.
I'm using python 2.7, but the behaviour seems to be the same under python 3.4.

As vaultah and Bhargav Rao reported in the comments, this is a known issue of python. I'll just have to find an alternative solution!
>>> my_id = str(3412)
>>> "{}/{}/{}".format(my_id[-1], my_id[-2], my_id)
'2/1/3412'

Python Xlrd Result format

i want to know, the result format of xlrd.
See the code
>>> sh.cell_value(rowx=2, colx=1)
u'Adam Gilchrist xxxxxxxxxxxxxxxxxxxxx'
Now when i try running a res.search
>>> temp1=sh.cell_value(rowx=2, colx=1)
>>> x=re.search("Adam",'temp1')
>>> x.group()
Traceback (most recent call last):
File "<pyshell#58>", line 1, in <module>
x.group()
AttributeError: 'NoneType' object has no attribute 'group'
I get nothing.
First i want to know , what is the 'u' with result.
What are the result formats returned by sh.cell_value. Is it integer, string etc.
Can we run regular expressions on them?

Answering your question first
First i want to know , what is the 'u' with result? u is the qualifier for unicode string. So u'Adam Gilchrist xxxxxxxxxxxxxxxxxxxxx' means the test in unicode.
What are the result formats returned by sh.cell_value . Is it integer , string etc.? Its unicode string
Can we run regular expressions on them ? Yes you can and this is how you do
temp1=u'Adam Gilchrist xxxxxxxxxxxxxxxxxxxxx'
x=re.search(u'Adam',temp1)
x.group()
u'Adam'
Its only that you have to specify the pattern in unicode also.

It's a Unicode string
Cell_value returns the value of the cell. The type depends on the type of the cell.
Yes. You can use regular expressions on Unicode strings, but your code isn't right.
Your code passes "temp1" to re.search as a string. It does not pass the variable temp1. You want:
>>> x=re.search(u"Adam",temp1)