What does %s mean in a python format string?

What does %s mean in a python format string?

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What does %s mean in Python? And what does the following bit of code do?

For instance...

 if len(sys.argv) < 2:
     sys.exit('Usage: %s database-name' % sys.argv[0])

 if not os.path.exists(sys.argv[1]):
     sys.exit('ERROR: Database %s was not found!' % sys.argv[1])

It is a string formatting syntax (which it borrows from C).

Please see "PyFormat":

Python supports formatting values into strings. Although this can include very complicated expressions, the most basic usage is to insert values into a string with the %s placeholder.

Edit: Here is a really simple example:

#Python2
name = raw_input("who are you? ")
print "hello %s" % (name,)

#Python3+
name = input("who are you? ")
print("hello %s" % (name,))

The %s token allows me to insert (and potentially format) a string. Notice that the %s token is replaced by whatever I pass to the string after the % symbol. Notice also that I am using a tuple here as well (when you only have one string using a tuple is optional) to illustrate that multiple strings can be inserted and formatted in one statement.

What does '%s' mean in python?, The role of %s is that it tells the python interpreter about what format text it will be printing, on the console. String is the format in this case. So the syntax goes  It's used to specify, in a dynamic way, what the width of the field is: The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted. so "indent" specifies how much space to allocate for the string that follows it in the parameter list. So, printf("%*s", 5, "");


Andrew's answer is good.

And just to help you out a bit more, here's how you use multiple formatting in one string

"Hello %s, my name is %s" % ('john', 'mike') # Hello john, my name is mike".

If you are using ints instead of string, use %d instead of %s.

"My name is %s and i'm %d" % ('john', 12) #My name is john and i'm 12

String Formatting - Learn Python, Python uses C-style string formatting to create new, formatted strings. Any object which is not a string can be formatted using the %s operator as well. Python uses C-style string formatting to create new, formatted strings. The "%" operator is used to format a set of variables enclosed in a "tuple" (a fixed size list), together with a format string, which contains normal text together with "argument specifiers", special symbols like "%s" and "%d".


The format method was introduced in Python 2.6. It is more capable and not much more difficult to use:

>>> "Hello {}, my name is {}".format('john', 'mike')
'Hello john, my name is mike'.

>>> "{1}, {0}".format('world', 'Hello')
'Hello, world'

>>> "{greeting}, {}".format('world', greeting='Hello')
'Hello, world'

>>> '%s' % name
"{'s1': 'hello', 's2': 'sibal'}"
>>> '%s' %name['s1']
'hello'

What does %s mean in a python format string?, %s is a string formatting syntax which it borrows from C. To know more about this you can have a look at the following video tutorial:- Intellipaat. In the replacement_field syntax notice the : preceding the format_spec. The field_name is optionally followed by a conversion field, which is preceded by an exclamation point '!', and a format_spec, which is preceded by a colon ':' When the field_name and/or conversion are specified, : marks the end of former and the start of the format_spec.


%s indicates a conversion type of string when using python's string formatting capabilities. More specifically, %s converts a specified value to a string using the str() function. Compare this with the %r conversion type that uses the repr() function for value conversion.

Take a look at the docs for string formatting.

What Does '%s' mean in Python? ~ TechnologyGist, The role of %s is that it tells the python interpreter about what format text it C-​styled string formatting can be notoriously tricky and sometimes  Re: {:}, you don't need the colon any more if there is no formatting to be done, as in 'hello {}'.format ("world") – cdarke Apr 11 '16 at 9:01. You can learn everything about Python string formatting in this cookbook - mkaz.tech/python-string-format.html – LearnerEarner Apr 11 '16 at 9:34. active oldest votes. Post Your Answer.


%sand %d are Format Specifiers or placeholders for formatting strings/decimals/floats etc.

MOST common used Format specifier:

%s : string

%d : decimals

%f : float

Self explanatory code:

name = "Gandalf"
extendedName = "the Grey"
age = 84
IQ = 149.9
print('type(name):', type(name)) #type(name): <class 'str'>
print('type(age):', type(age))   #type(age): <class 'int'>   
print('type(IQ):', type(IQ))     #type(IQ): <class 'float'>   

print('%s %s\'s age is %d with incredible IQ of %f ' %(name, extendedName, age, IQ)) #Gandalf the Grey's age is 84 with incredible IQ of 149.900000 

#Same output can be printed in following ways:


print ('{0} {1}\'s age is {2} with incredible IQ of {3} '.format(name, extendedName, age, IQ))          # with help of older method
print ('{} {}\'s age is {} with incredible IQ of {} '.format(name, extendedName, age, IQ))          # with help of older method

print("Multiplication of %d and %f is %f" %(age, IQ, age*IQ)) #Multiplication of 84 and 149.900000 is 12591.600000          

#storing formattings in string

sub1 = "python string!"
sub2 = "an arg"

a = "i am a %s" % sub1
b = "i am a {0}".format(sub1)

c = "with %(kwarg)s!" % {'kwarg':sub2}
d = "with {kwarg}!".format(kwarg=sub2)

print(a)    # "i am a python string!"
print(b)   # "i am a python string!"
print(c)    # "with an arg!"
print(d)   # "with an arg!"

Python 3's f-Strings: An Improved String Formatting Syntax (Guide , As of Python 3.6, f-strings are a great new way to format strings. You are %s. to make sure you include at least one of those methods in your class definition. print(' {:^{}}'.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:


% (String Formatting Operator), If format specifier is a Unicode object, or if any of the objects being converted using the %s conversion are Unicode objects, the result will also be a Unicode object. I don't understand what %s and %d do and how they work. They are used for formatting strings. %s acts a placeholder for a string while %d acts as a placeholder for a number. Their associated values are passed in via a tuple using the % operator. will print marcog 42. Note that name is a string (%s) and number is an integer (%d for decimal).


6.1. string — Common string operations, The return value used_key has the same meaning as the key parameter to get_value(). If the numerical arg_names in a format string are 0, 1, 2, in "​Harold's a clever {0!s}" # Calls str() on the argument first "Bring out the  When placeholders { } are empty, Python will replace the values passed through str.format() in order. The values that exist within the str.format() method are essentially tuple data types and each individual value contained in the tuple can be called by its index number, which starts with the index number 0. These index numbers can be passes into the curly braces that serve as the placeholders in the original string.


Python String Formatting, Prefer f-strings when working in a codebase that supports it - meaning, all developers and end-users of the code base are certain to have Python 3.6 or later. Until  Python’s str.format () method of the string class allows you to do variable substitutions and value formatting. This lets you concatenate elements together within a string through positional formatting. This tutorial will guide you through some of the common uses of formatters in Python, which can help make your code and program more readable