Yes, but you have to pass them in as arguments to format, and then refer to them wrapped in {} like you would the argument name itself:

print('\n{:^{display_width}}'.format('some text here', display_width=display_width))

Or shorter but a little less explicit:

print('\n{:^{}}'.format('some text here', display_width))

Since this question was originally posted, Python 3.6 has added f-strings, which allow you to do this without using the format method and it uses variables which are in scope rather than having to pass in the named variables as keyword arguments:

display_width = 50
text = 'some text here'
print(f'\n{text:^{display_width}}')

You can use locals() function

s="svn cp {root_dir}/{trunk}/{root_dir}/{tag}/".format(**locals())

EDIT:

Since python 3.6 you can use string interpolation:

s = f"svn cp {root_dir}/{trunk}/{root_dir}/{tag}/"

Dynamically creating global variables can get hairy. It is much easier if you put it in a smaller scope ==> any object, e.g., a dictionary. You can achieve what you want like this

my_dictionary = dict()
for f in features:
    my_dictionary['report_{}'.format(f)] = pd.DataFrame(index=data[f].unique(),columns=['Prediction','Actual'])

You can access the df like my_dictionary['report_Gender'] for example.

Another way would be to create a class:

class Reports:
    pass

for f in features:
    setattr(Reports, 'report_{}'.format(f), pd.DataFrame(index=data[f].unique(),columns=['Prediction','Actual'])

Then access as Reports.report_Gender etc...

See Python PEP 8: Function and Variable Names:

Function names should be lowercase, with words separated by underscores as necessary to improve readability.

Variable names follow the same convention as function names.

mixedCase is allowed only in contexts where that's already the prevailing style (e.g. threading.py), to retain backwards compatibility.

You can parse the format yourself with the string.Formatter() class to list all references:

from string import Formatter

names = [fn for _, fn, _, _ in Formatter().parse(yourstring) if fn is not None]

Demo:

>>> from string import Formatter
>>> yourstring = "My name is {myname}"
>>> [fn for _, fn, _, _ in Formatter().parse(yourstring) if fn is not None]
['myname']

You could subclass Formatter to do something more fancy; the Formatter.get_field() method is called for each parsed field name, for example, so a subclass could work harder to find the right object to use.

You can use the str.format() method, which lets you interpolate other variables for things like the width:

'Number {i}: {num:{field_size}.2f}'.format(i=i, num=num, field_size=field_size)

Each {} is a placeholder, filling in named values from the keyword arguments (you can use numbered positional arguments too). The part after the optional : gives the format (the second argument to the format() function, basically), and you can use more {} placeholders there to fill in parameters.

Using numbered positions would look like this:

'Number {0}: {1:{2}.2f}'.format(i, num, field_size)

but you could also mix the two or pick different names:

'Number {0}: {1:{width}.2f}'.format(i, num, width=field_size)

If you omit the numbers and names, the fields are automatically numbered, so the following is equivalent to the preceding format:

'Number {}: {:{width}.2f}'.format(i, num, width=field_size)

Note that the whole string is a template, so things like the Number string and the colon are part of the template here.

You need to take into account that the field size includes the decimal point, however; you may need to adjust your size to add those 3 extra characters.

Demo:

>>> i = 3
>>> num = 25
>>> field_size = 7
>>> 'Number {i}: {num:{field_size}.2f}'.format(i=i, num=num, field_size=field_size)
'Number 3:   25.00'

Last but not least, of Python 3.6 and up, you can put the variables directly into the string literal by using a formatted string literal:

f'Number {i}: {num:{field_size}.2f}'

The advantage of using a regular string template and str.format() is that you can swap out the template, the advantage of f-strings is that makes for very readable and compact string formatting inline in the string value syntax itself.

Named replacement fields (the {...} parts in a format string) match against keyword arguments to the .format() method, and not positional arguments.

Keyword arguments are like keys in a dictionary; order doesn't matter, as they are matched against a name.

If you wanted to match against positional arguments, use numbers:

"{0} {1}".format(10, 20)

In Python 2.7 and up, you can omit the numbers; the {} replacement fields are then auto-numbered in order of appearance in the formatting string:

"{} {}".format(10, 20) 

The formatting string can match against both positional and keyword arguments, and can use arguments multiple times:

"{1} {ham} {0} {foo} {1}".format(10, 20, foo='bar', ham='spam')

Quoting from the format string specification:

The field_name itself begins with an arg_name that is either a number or a keyword. If it’s a number, it refers to a positional argument, and if it’s a keyword, it refers to a named keyword argument.

Emphasis mine.

If you are creating a large formatting string, it is often much more readable and maintainable to use named replacement fields, so you don't have to keep counting out the arguments and figure out what argument goes where into the resulting string.

You can also use the **keywords calling syntax to apply an existing dictionary to a format, making it easy to turn a CSV file into formatted output:

import csv

fields = ('category', 'code', 'price', 'description', 'link', 'picture', 'plans')
table_row = '''\
    <tr>
      <td><img src="{picture}"></td>
      <td><a href="{link}">{description}</a> ({price:.2f})</td>
   </tr>
'''

with open(filename, 'rb') as infile:
    reader = csv.DictReader(infile, fieldnames=fields, delimiter='\t')
    for row in reader:
        row['price'] = float(row['price'])  # needed to make `.2f` formatting work
        print table_row.format(**row)

Here, picture, link, description and price are all keys in the row dictionary, and it is much easier to see what happens when I apply the row to the formatting string.