How to f string in python
Python Quick Tip: F-Strings - How to Use Them and Advanced String Formatting
Timecodes:
hey there how's it going everybody now
this is going to be a quick video where
I show you a feature that you've likely
seen me use and a lot of my videos so
far and that is F string so f strings
are a new way to format strings in
Python 3.6 and above and I prefer using
them over any other formatting methods
so if you're not using Python 3.6 or
higher then you'll need to install that
in order to follow along with this video
okay so let's take a couple of examples
and see why I prefer using these so
first of all I have two variables here
at the top so I have first name and last
name so let's say that I wanted to print
a sentence that says my name is and then
include the first name and last name in
that string now the way you've probably
been familiar with doing this is with
the format method and this is how I used
to do it too as well so we have our
curly braces here as placeholders and
then we're using our format method to
feel in the placeholders with these
values so the first name is going to put
get put in the first placeholder here
and the last name is going to get put in
the second place holder here now if any
of this is unfamiliar to you then I do
have an older video where I go in-depth
on how to use the format method that
goes over a lot of these same examples
that I'm going to use in this video with
F strings so if you're curious then you
can watch that first okay so this should
work how I have it right now with this
format method so if I save this and run
it then you can see that we did get our
sentence with our values that we wanted
but right now this is not extremely
elegant or intuitive so for example if
we have a lot of placeholders then we
kind of have to go back and forth to see
what placeholders match up with what
values so I'd have to go back and forth
between the format method here and the
placeholder to see where what is going
to get filled in where but now let's see
what this looks like using an F string
so I'm going to comment out what we have
here and I'm going to uncomment out the
section here and I'll bring this up one
so so far here I have a sentence that
has our two placeholders and I've
removed the format method
now instead we're simply going to use an
F string and to specify that we want
this to be an F string then we just put
an F in front of the string here to tell
Python that this is going to be an F
string a formatted string and now
instead of using the format method we
can simply add our variables directly
into our placeholders so within the
curly braces here I'm going to say first
name and within the second one here I'm
going to say last name so if I save this
and run it then you can see that we get
the same result and that this works but
also look at how much more intuitive
this looks we no longer have to go back
and forth between our placeholders and
the format method to see what will be
added where we can just look at this
directly and see that our string will be
equal to my name is and then our first
name and then followed by space and then
our last name now another cool thing is
that we can actually run functions or
methods directly within the EPS string
so let's say that we wanted our first
and last name to be capitalized so to do
that we could simply come in here and
say first name dot upper and also say
last name dot upper and if I save that
and run it that you can see then our
output it says my name is and then it
capitalized our first name and last name
so I personally think that that's
extremely simple and a lot easier to
read than if these were in a format
method okay so let's take a look at how
we would print out some dictionary
values using an F string so I'm going to
remove all of this and uncomment out
this section here so I have a dictionary
here and the dictionary just has a key
of name with a value of gin and a key of
age with a value of 23 and now I have
another sentence here where we have a
couple of placeholders and I'm using a
format method for now and to the first
placeholder we're passing in this person
and accessing that name key which should
be gin and the second value here we are
putting
the person and accessing that h key
which should be 23 so this sentence
should say my name is Jen and I am 23
years old so this is how we would do
this with the format method so if I save
this and run it then you can see that
that works fine but now let's see how we
do this with an F string so I'm going to
comment out that and uncomment out our
second part here so we have our string
with our placeholders and we also have
our F at the beginning to specify that
this is an F string now there is one
thing that we need to watch out for here
now since we are now going to access the
keys directly within the string we now
have to figure out what to do with the
quotes we're using to access that key so
let me show you what I mean so if I try
to just put this in directly into our
placeholder like we did before so I'll
say person and access our name and then
also person and access the age then our
single quotes that we're using here to
access our key to our dictionary is
terminating our string early because we
opened our string with a single quote as
well so if I run this then it should
give me a syntax error and it does it
says invalid syntax so to avoid this if
you're using single quotes inside of
your F string then simply use double
quotes to open and close your string
then the single quotes will no longer
conflict with those and I do this with
normal strings as well I'd rather change
the quotes than look at a bunch of
escape sequences and stuff like that so
let me change the opening and closing
quotes so if I come in here I'll just
open this with a double quote and I will
close that with a double quote and now
our single quotes are no longer
affecting the opening or closing of our
string so now if I save this and run it
then you can see that that works fine
okay so now let me show you a few other
things that we can do before ending this
video so let me uncomment out this line
here so like I said we can run functions
and methods from directly within the F
string but we can also do calculations
so in this example I
and simply go into our placeholder so
our string says four times eleven is
equal to and I can simply go in our
placeholder and say four times eleven
and then I can save that and run it and
we can see that within our F string it
did that calculation so it says four
times eleven is equal to forty four now
we can also do some more advanced
formatting and our F strings as well so
in this next example let me uncomment
out this in this example I am looping
through a range of values of one through
ten and I am just printing those out
through each loop so I'm printing out
the value of n each time we go through
the loop so if I save this and run it
then we can see that our result is the
value is 1 by use 2 and so on but let's
say that I wanted each of these values
to be 0 padded by a certain amount so
sometimes it can be important to 0 pad
values when adding them to a database or
to expect a certain length or anything
like that so to do this we can go up
into our F string here and just put a
colon after our value to specify that
we're going to do some additional
formatting and now if we wanted to 0 pad
by 2 digits then we can simply say 0 to
specify 0 padding and then 2 for 2
digits so if I save that and run it then
now we can see in our loop here that all
of our values have a leading 0 except
for the 10 because it's already two
digits so if we wanted to 0 pad by 3 or
4 digits or whatever then you can simply
change this 2 to whatever you'd like so
if I change that to a 4 save it and run
it you can see that now we are Z 0
padded with four digits total okay so
now let's move on to floating point
values so let me get rid of that and
oncome and uncomment this section here
okay so here I have pi written out to a
certain number of values and in our
string we are simply printing that out
so we have an F string here that says pi
is equal to and then just printing out
pi so if I save that and run it then we
can see that that works but what if that
is a longer floating point number
than what we want to print so let's say
that we want to print two four digits
than to do this we can put a colon after
our value here and the place holder like
we did before to specify that we're
going to do some extra formatting and
now we to specify that we want to only
print up to four digits then we can say
point here a dot to specify a floating
point and then I'll say four four four
digits and then an F for a floating
point value so I'll save that and run it
and you can see that now we have a
precision of four that we're printing
out this value and we can see that it
also rounded this up correctly so it's
not just chopping that value off and
again if you'd like to change the
precision then you can simply change
that forward to any value that you'd
like so if I do five save that and run
it then you can see that now it's five
digit precision there okay so lastly
let's take a quick look at formatting
and printing dates so I'll get rid of
that there and come down here and
uncomment out this section and I'll
separate out the import statement there
now this is probably the kind of
formatting that I use most often because
the way that we want to display dates
can vary so much okay so I have created
a date time here that is a fake birthday
of January 1st 1990 and we can see that
we're currently just passing this date
time directly into our placeholder in
our F string and printing that out so
let's see what that looks like by
default so if I save this and run it
then we can see that it says jen has a
birthday on 1991 one and then the
minutes and seconds there so we can see
that that's not the best-looking output
now we can read it but it would be nice
if we could change this to whatever we'd
like so let's say that I wanted to this
to literally output you know Jen has a
birthday on January 1st 1990 now to do
this we're gonna have to know the
date/time formatting codes and I never
remember these I'm constantly needing to
look them up but if we go to our site
here this is just the Python
documentation
here in section eight point one point
eight towards it's basically towards the
bottom of the date-time documentation
and this will give you the codes for
whatever output you want so for example
we can see that the percent sign
uppercase B here is the code for the
entire month spelled out and it gives
some examples here and the lowercase B
here is an abbreviated month so remember
for our output I wanted it to say
January 1st 1990 so what we're gonna
want is this uppercase B to spell out
January and then it looks like this
lowercase D is the day and then for the
year we want this capital Y to do a
four-digit year this lowercase Y is just
a two-digit year without the century so
we're going to go with the uppercase Y
so let's go back to our example and now
let's fill in these values to format our
string how we like so just like we've
seen before I'm going to add a colon
after our value to specify that we want
to do some additional formatting here
and now we can just type in how we want
this to look using those codes that we
solve from the documentation so I'm
gonna say % b2 have the month first and
then a space and then % D to give the
day and then I'm going to do a comma
after the day and then to do the year
that's going to be % uppercase Y so now
if I save this and run it then we can
see that it says Jin has a birthday on
January 1st comma 1990 so we can see
that we got the formatting that we were
hoping for and that that worked well ok
so I think that is going to do it for
this video hopefully now you have a good
idea for how you can use f strings and
if you see me using it in future videos
then nothing will throw you off but if
you do have any questions about what we
covered in this video then feel free to
ask in the comment section below and
I'll do my best to answer those and if
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