How to get the variable names from the string for the format() method

Question

Lets say I have this line:

"My name is {name}".format(name="qwerty")

I know that the variable name is name and so I can fill it. But what if the word inside the {} always changes, like this:

"My name is {name}"
"My name is {n}"
"My name is {myname}"

I want to be able to do this:

"My name is {*}".format(*=get_value(*))

Where * is what ever word was given inside the {}

Hope I was clear.

EDIT:

def get_value(var):
    return mydict.get(var)

def printme(str):
    print str.format(var1=get_value(var1), var2=get_value(var2))

printme("my name is {name} {lastname}")
printme("your {gender} is a {sex}")

Having this, I can't hard code any of the variables inside printme function.

Martijn Pieters · Accepted Answer · 2014-04-03 07:17:10Z

43

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.

answered Apr 3, 2014 at 7:17

Martijn Pieters

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7 Comments

MichaelR Over a year ago

But now, how do i use names in the format method to get all the values?

Martijn Pieters Over a year ago

@MichaelR: How were you planning to pair up the names with values? You can always use dict(zip(names, values)) to create a dictionary, provided you know many values you need to provide.

Martijn Pieters Over a year ago

@MichaelR: yourstring.format(**dict(zip(names, values))).

MichaelR Over a year ago

I wanted to use this: yourstring.format([(i,get_value(i)) for i in names]) but it gives me an error for some reason :-\

Martijn Pieters Over a year ago

Right; you'd still have to build a dictionary; yourstring.format(**{i: get_value(i) for i in names}) if you are on Python 2.7 or newer.

|

Flair · Accepted Answer · 2021-08-16 08:53:59Z

4

Python 3.8 added an awesome solution for this using f-strings:

my_var = 123
print(f"{my_var = }")

Which will print

my_var = 123

edited Aug 16, 2021 at 8:53

Flair

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answered Aug 15, 2021 at 17:57

Andrew Wilson

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2 Comments

axolotl Over a year ago

what's happening here? is this a special syntax within f-strings? my_var = doesn't evaluate to a valid python expression, so it must be that string formatting is treating this construction differently. I had no idea this was possible!

axolotl Over a year ago

looks documented here: docs.python.org/3/whatsnew/…

Nishant Nawarkhede · Accepted Answer · 2014-04-03 07:16:01Z

1

You can use variable instead of name="querty"

name1="This is my name";

>>"My name is {name}".format(name=name1)

Output:

'My name is abc'

Another example ,

a=["A","B","C","D","E"]
>>> for i in a:
...     print "My name is {name}".format(name=i)

Output:

My name is A
My name is B
My name is C
My name is D
My name is E

edited Apr 3, 2014 at 7:16

answered Apr 3, 2014 at 7:10

Nishant Nawarkhede

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Comments

Saurabh Chandra Patel · Accepted Answer · 2020-12-08 14:56:18Z

0

def get_arg(yourstring):
    arg_list = []
    pin = False
    for ch in yourstring:
        if ch == "{":
            pin = True
        elif ch == "}":
            pin = False
            arg_list.append(text)
            text = ""
        elif pin:
            text +=ch
    return arg_list

answered Dec 8, 2020 at 14:56

Saurabh Chandra Patel

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Comments

Mihai Zamfir · Accepted Answer · 2014-04-03 07:10:34Z

-1

Or an alternative is to use a function:

def format_string(name):
    return "My name is {name}".format(name="qwerty")

Then call it:

format_string("whatever")

answered Apr 3, 2014 at 7:10

Mihai Zamfir

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Comments

Matthias · Accepted Answer · 2014-04-03 07:51:43Z

-1

If your data is in a dictionary (according to your edited question) then you can use the dictionary as a parameter for format.

data = {'first_name': 'Monty',
        'last_name': 'Python'}

print('Hello {first_name}'.format(**data))
print('Hello {last_name}'.format(**data))

answered Apr 3, 2014 at 7:51

Matthias

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