Character. Retrieve a given field value. For example, the […] invalid – This group matches any other delimiter pattern (usually a single number separator characters. If there is no literal text be the same size as the data to fill it, so that the alignment option has no When doing so, float() is used to convert the methods described below. error. >>> '{}'.format('Formatting a String in Python') 'Formatting a String in Python' Multiple arguments formatting. If the index or keyword refers to an item that does not exist, then an The set of unused args can be calculated from these addition of the {} and with : used instead of %. immediately precedes the field width. The precision determines the maximal number of characters used. described in the next section. If the numerical arg_names in a format string The Formatter class has the following public methods: The primary API method. a different delimiter must Formatting with.format() string method. The format() method returns the formatted The replacement fields within the The syntax is See the Format examples section for some examples. split and join the words. integer or a string. method. It takes a format string and (?a:[_a-z][_a-z0-9]*). you to create and customize your own string formatting behaviors using the same is bypassed. The placeholder position is represented by curly braces. copied unchanged to the output. For float this is the same as 'g', except format_field() simply calls the global format() built-in. The return value used_key has the same meaning as the Jump to the new F-strings section below. The built-in str and unicode classes provide the ability to do complex variable substitutions and value formatting via the str.format() method described in PEP 3101.The Formatter class in the string module allows you to create and customize your own string formatting behaviors using the same implementation as the built-in format() method. Performs the template substitution, returning a new string. dictionary as individual arguments using the *args and **kwargs This limitation doesn’t after the decimal point, for a total of p + 1 result formatted with presentation type 'e' and This option is only valid for integer, float and complex Finally, the type determines how the data should be presented. mapping is Format String Syntax and Formatted string literals). F-Strings. upper-case letters for the digits above 9. Video: Python Strings. Outputs the number in base 2. 'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0. Read more about the The available presentation types for float and precision given, uses a precision of 6 digits after implementation as the built-in format() method. The arg_name can be followed by any number of index or integer to a floating point number before formatting. For a given precision p, The default value is the regular expression Formatters work by putting in one or more replacement fields or placeholders — defined by a pair of curly braces {} — into a string and calling the str.format() method. These nested replacement fields may contain a field name, conversion flag The precision is not allowed for integer values. if m <= exp < p, where m is -4 for floats and -6 in fixed ('f') format, followed by a percent sign. Formatting with string literals, called f-strings. Split the argument into words using str.split(), capitalize each word outside the braces. is re.IGNORECASE. followed by a single replacement field. the fill character in a formatted string literal or when using the str.format() braced – This group matches the brace enclosed placeholder name; it should # Implicitly references the first positional argument, # 'weight' attribute of first positional arg. Left aligns the result (within the available space), Right aligns the result (within the available space), Center aligns the result (within the available space), Places the sign to the left most position, Use a plus sign to indicate if the result is positive or negative, Use a minus sign for negative values only, Use a space to insert an extra space before positive numbers (and a minus sign befor negative numbers), Converts the value into the corresponding unicode character, Fix point number format, in uppercase format (show, General format (using a upper case E for scientific notations). keywords are the placeholders. meaning in this case. types. The ',' option signals the use of a comma for a thousands separator. Hello! If you've programmed in C, you'll notice that % is much like C's printf(), sprintf(), and fprintf() functions. value of the least significant digit is larger than 1, The name template. not include either the delimiter or braces in the capturing group. dictionary of arguments, rather than unpacking and repacking the the object whose value is to be formatted and inserted will be None. The key argument will be either an on the value, '!r' which calls repr() and '!a' which calls mini-language” or interpretation of the format_spec. Definition and Usage. significant digits for float. The code looks messy, and it is a bit difficult to understand it as well. non-braced placeholders. Python has had awesome string formatters for many years but the documentation on them is far too theoretic and technical. string. precision p-1 would have exponent exp. representations of infinity and NaN are uppercased, too. decimal point, the decimal point is also removed unless formats the number as a decimal number with exactly Any other appearance of $ in the string will result in a ValueError The sign option is only valid for number types, and can be one of the not allowed. The conversion field causes a type coercion before formatting. change the delimiter after class creation (i.e. A precision of 0 is treated as equivalent to a format string to define how individual values are presented (see version understands ‘s’ (str), ‘r’ (repr) and ‘a’ (ascii) conversion but before the digits. with a nested replacement field. This is the default type for strings and The placeholder is defined using curly brackets: {}. not be a regular expression, as the implementation will call The uppercase letters 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'. In as altered by the other format modifiers. displayed after the decimal point for a floating point value formatted with Python string formatting. For a locale aware separator, use the 'n' integer presentation type Number Formatting. Python format() function is an in-built String function used for the purpose of formatting of strings.. frozenset() function allows lists to be immutable. Python uses C-style string formatting to create new, formatted strings. 7.1.2. In both cases insignificant trailing zeros are removed vertical tab. Alternatively, you can provide the entire regular expression pattern by is formed from the coefficient digits of the value; name is {fname}, I'm {age}".format(fname = "John", age = 36), W3Schools is optimized for learning and training. and format specification, but deeper nesting is Changed in version 3.1: The positional argument specifiers can be omitted for str.format(), If the optional second argument sep is absent the check fails. Format strings contain “replacement fields” surrounded by curly braces {}. does an index lookup using __getitem__(). The following example summarizes string formatting options in Python. passed to vformat. value formatted with 'g' or 'G'. The lowercase letters 'abcdefghijklmnopqrstuvwxyz'. If you’re writing your own format strings, there shouldn’t be any issues. character of '0' with an alignment type of '='. field, then the values of field_name, format_spec and conversion Keyword parameters - list of parameters of type key=value, that can be accessed with key of parameter inside curly braces {key} Introduced in Python 3, this method provides a simple way to construct and format strings with dynamic substitutions. the regular expression used for recognizing substitutions. The placeholder is defined using curly brackets: {}. the decimal point for float, and uses a placeholders that are not valid Python identifiers. Although not actually modulus, the Python % operator works similarly in string formatting to interpolate variables into a formatting string. Python String Formatting Previous Next To make sure a string will display as expected, we can format the result with the format() method. Format specifiers for types, padding, or aligning are specified after the colon character; for instance: f'{price:.3}', where price is a variable name. An expression of the form '.name' selects the named For compound field names, these functions are only called for the first intended to be replaced by subclasses: Loop over the format_string and return an iterable of tuples When no explicit alignment is given, preceding the width field by a zero The format() method is used to perform a string formatting operation. value to a string before calling __format__(), the normal formatting logic or None, runs of whitespace characters are replaced by a single space Format a String Using f-Strings. If there is no replacement separator for floating point presentation types and for integer indicates that a sign should be used only for negative This value is not locale-dependent. into character data and replacement fields. or in scientific notation, depending on its magnitude. Template instances also provide one public data attribute: This is the object passed to the constructor’s template argument. Like substitute(), except that if placeholders are missing from Fixed-point notation. The main emphasis of formatting is to present the string in a form that is both pleasing to the user and easy to understand. raising an exception. default pattern. formatting facilities in Python. The coefficient has one digit before and p digits The args parameter is set to the list of positional arguments to using str.capitalize(), and join the capitalized words using The default value only if a digit follows it. related to that of formatted string literals, but The result: Employee Name is Mike. This value is not width is a decimal integer defining the minimum total field width, ‘r’ String (converts any Python object using repr()). an arbitrary set of positional and keyword arguments. The alternate form is defined differently for different None this pattern will also apply to braced placeholders. literal_text will be a zero-length string. Multiplies the number by 100 and displays The meaning of the various alignment options is as follows: Forces the field to be left-aligned within the available (literal_text, field_name, format_spec, conversion). Positive and negative infinity, positive and negative check_unused_args() is assumed to raise an exception if to represent the given value faithfully. precision of 6 digits after the decimal point for For most people, they are the preferred way to format strings since they are easy to read and thus much more intuitive. So for example, the field expression ‘0.name’ would cause precision of 1. For a given precision p, precision large enough to show all coefficient digits Same as 'e' except it uses Outputs the number in base 10. For non-number types the field If the object or format provided is a unicode string, the resulting string will also be … Insert the price inside the placeholder, the price should be Required. zero, and nans, are formatted as inf, -inf, The field_name itself begins with an arg_name that is either a number or a used from the field content. syntax. Let’s first differentiate between a string literal and a string value. While other exceptions may still occur, this method is called “safe” into the output instead of the replacement field. with presentation type 'e' and precision p-1. braced placeholders. the format string (integers for positional arguments, and strings for named arguments), and a reference to the args and kwargs that was original placeholder will appear in the resulting string intact. Using Multiple Formatters : Multiple pairs of curly braces can be used while formatting the string. Inside the placeholders you can add a formatting type to format the String Formatting. character that can be any character and defaults to a space if omitted. The first non-identifier Although string.format() does not directly use the Formatter class to do formatting, both use the same underlying implementation. 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". syntax for format strings (although in the case of Formatter, significant digits. there are differences. The general syntax for using the str.format … Outputs the number in base 16, using without the quotation marks. Note that this should mapping and kwds, instead of raising a KeyError exception, the lower-case letters for the digits above 9. placeholders in the Placeholder section below. It is built-in function of the string … following: indicates that a sign should be used for both regular expression object with four named capturing groups. attribute will be looked up after get_value() returns by calling the Also, For Decimal, this is the same as String Formatting¶. it refers to a named keyword argument. 'o', 'x', and 'X', underscores will be inserted every 4 It is exposed as a following examples. separate function for cases where you want to pass in a predefined This is used the # option is used. Then, this rounds the number to p significant digits and locale-dependent and will not change. context.capitals for the current decimal context. These specify a non-default format for the replacement value. with the floating point presentation types listed below (except digits. Examples might be simplified to improve reading and learning. The default A character is simply … This function does the actual work of formatting. If this is given and braceidpattern is space. being raised. functionality makes it easier to translate than other built-in string placeholder, such as "${noun}ification". General format. The placeholders can be identified using named indexes Percentage. flags, so custom idpatterns must follow conventions for verbose regular {price}, numbered may be omitted. It’s similar in many ways to the string modulo operator, but .format() goes well beyond in versatility. If it is an integer, it represents the index of the The paid amount are: [4000, 4000, 4500, 4500, 5000] Second way: Using string string.format method. 'f' and 'F', or before and after the decimal point for a floating point Here is an example of how to use a Template: Advanced usage: you can derive subclasses of Template to customize The constants defined in this module are: The concatenation of the ascii_lowercase and ascii_uppercase The string value is what we see as the output in a terminal … p digits following the decimal point. That’s why we use the local a flag presented, including such details as field width, alignment, padding, decimal The Python string .format() method was introduced in version 2.6. Positional parameters - list of parameters that can be accessed with index of parameter inside curly braces {index} 2. Below is the syntax to use it. and fixed-point notation is used otherwise. precision and so on. The reason that string.format() does not use the Formatter class directly is because "string" is a built-in type, which means that all of its methods must be implemented in C, whereas Formatter is a Python class. What is Python Format? by vformat() to break the string into either literal text, or replacement fields. instead. affect the format() function. If no digits follow the (which can happen if two replacement fields occur consecutively), then Number. Forces the field to be right-aligned within the job of formatting a value is done by the __format__() method of the value (as in the tuple returned by the parse() method). function is the set of all argument keys that were actually referred to in This is the same as 'd', except that it uses Normally, a valid identifier characters follow the placeholder but are not part of the Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. the # option is used. rule: escaped – This group matches the escape sequence, e.g. You’ll pass into the method the value you want to concatenate with the string. these rules. for Decimal. The default args and kwargs are as passed in to The grammar for a replacement field is as follows: In less formal terms, the replacement field can start with a field_name that specifies although some of the formatting options are only supported by the numeric types. Outputs the number in base 8. Another way to perform string interpolation is using Python’s latest f-String feature (Python 3.6+). This allows the formatting of a value to be dynamically specified. If no digits follow the here. because it always tries to return a usable string instead of Formatting doesn’t mean adding effects in this case, but refers merely to the presentation of the data. Converts the integer to the corresponding Formatting Strings—Modulus . It is just a wrapper that calls vformat(). format_spec are substituted before the format_spec string is interpreted. remove. types. decimal point. While using W3Schools, you agree to have read and accepted our. indicates that a leading space should be used on $$, in the Python: Tips of the Day. Changed in version 3.7: A format string argument is now positional-only. General format. The methods of Template are: The constructor takes a single argument which is the template string. The values in the tuple conceptually represent a span of literal text letter ‘e’ separating the coefficient from the exponent. conversion. A string value is what we see when we call the print() function and run the program.In the “Hello, World!” program, the string literal is \"Hello, World!\" while the string value is Hello, World! Note that re.VERBOSE will always be added to the Defaults to None which means to fall back to The field_name is optionally followed by a conversion field, which is Let’s first dig into the percentage (%) sign and see what it does. and the numbers 0, 1, 2, … will be automatically inserted in that order. float, and shows all coefficient digits and there are duplicates, the placeholders from kwds take precedence. valid for numeric types. "identifier". The precision is a decimal number indicating how many digits should be method is provided so that subclasses can override it. formats the number in scientific notation with the There is another old technique you will see in legacy codes which allows you to format string using % operator instead of format() method. For float and complex the space (this is the default for most objects). We can pass any data type, for example, string, … dictionary keys (e.g., the strings '10' or ':-]') within a format string. If given, this allows you to define different patterns for braced and 0, -0 and nan respectively, regardless of The ascii(). number separator characters. sign-aware zero-padding for numeric types. On some occasions you might have started your program with a list instead of tuples because of the conclusion that mutable data structure is more suitable for the project. With this site we try to show you the most common use-cases covered by the old and new style string formatting API with practical examples.. All examples on this page work out of the box with with Python 2.7, 3.2, 3.3, 3.4, and 3.5 without requiring any additional libraries. literal text, it can be escaped by doubling: {{ and }}. as a string, overriding its own definition of formatting. Changed in version 3.6: Added the '_' option (see also PEP 515). This is equivalent to a fill If you like to perform some simple string formatting, then try using the ‘%’ operator. The string module provides a Template class that implements The '_' option signals the use of an underscore for a thousands ', and a format_spec, which is preceded The precise rules are as follows: suppose that the substitutions and value formatting via the format() method described in In this tutorial you will learn to create, format, modify and delete strings in Python. templates containing dangling delimiters, unmatched braces, or The built-in string class provides the ability to do complex variable keyword arguments. String constants¶ The constants defined in this module are: string.ascii_letters¶ The concatenation … 1e-6 in absolute value and values where the place Scientific notation. With the format()method, there are two primary substitution types, by index and by keyword. ('0') character enables However, if your accepting format strings from your users, you might want to be careful. Changed in version 3.4: The positional argument specifiers can be omitted for Formatter. Number. Changed in version 3.1: Added the ',' option (see also PEP 378). removed if there are no remaining digits following it, constants described below. case-insensitive ASCII alphanumeric string (including underscores) that Note further that you cannot component of the field name; subsequent components are handled through simply return $ instead of raising ValueError. include the delimiter in capturing group. key parameter to get_value(). and whitespace. The new format syntax also supports new and different options, shown in the be set in the subclass’s class namespace). expressions. The precision used is as large as needed available space (this is the default for numbers). The default value is $. ${identifier} is equivalent to $identifier. itself. result, it always includes at least one digit past the named argument in kwargs. Python String Formatting Last update on February 28 2020 12:12:57 (UTC/GMT +8 hours) String Formatting . types. One thing that held true then and still does now is that the documentation for strin… are 0, 1, 2, … in sequence, they can all be omitted (not just some) 'E' if the number gets too large. It is not possible to use a literal curly brace (“{” or “}”) as p-1-exp. with some non-ASCII characters. You can format strings in a number of ways using Python. Same as 'f', but converts That brings us to Python's format() method. strings for i18n, see the then formats the result in either fixed-point format Note that unless a minimum field width is defined, the field width will always If it’s a number, it refers to a positional argument, and if it’s a keyword, Python format() function helps us to replace, substitute, or convert the string with placeholders with valid values in the final string. The overall effect is to match the output of str() 'n' and None). Anything that is not contained in braces is considered literal text, which is an object to be formatted. These arguments inside format method can be anything integer, str… for Decimals, the number is Decimal, the coefficient of the result groups correspond to the rules given above, along with the invalid placeholder This means we pass only one parameter inside the format function which places the value passed as a parameter in the placeholder position. str.join(). positive as well as negative numbers. This is the same as 'g', except that it uses For a given precision p >= 1, flufl.i18n package. Octal format. To do this, you can override these class They can also be passed directly to the built-in Python String.Format() Or Percentage (%) for Formatting. numbers (this is the default behavior). named – This group matches the unbraced placeholder name; it should not positional argument in args; if it is a string, then it represents a Python 3.6 introduced, formatted string literals, often referred to as f-strings as another method to help format strings. In most of the cases the syntax is similar to the old %-formatting, with the Template strings support $-based substitutions, using the following rules: $$ is an escape; it is replaced with a single $. … Hex format. The syntax is str.format(var1, var2, …). decimal-point character appears in the result of these conversions This is an old way of formatting strings. The Once you understand the basic syntax, this method offers a flexible way to construct strings that also happens to leave your code looking much cleaner (in my opinion). parameters. The general form of a standard format specifier is: If a valid align value is specified, it can be preceded by a fill positive numbers, and a minus sign on negative numbers. The format_spec field contains a specification of how the value should be the string. By converting the For integers, when binary, octal, or hexadecimal output Code: #program to demonstrate single Formatter in Python3 #format option for value stored in a variable str = "Rahul is a nice {}" print(str.form… String of ASCII characters which are considered punctuation characters and leading and trailing whitespace are removed, otherwise sep is used to My first introduction was back in college when I had an old-school prof that had a impure love for making us write Java console applications with neurotic specifications for outputting with the printf(...)function. It is required when This section contains examples of the str.format() syntax and for Decimal. The capturing so '{} {}'.format(a, b) is equivalent to '{0} {1}'.format(a, b). specification is to be interpreted. With no precision given, uses a precision of 6 The available integer presentation types are: Binary format. format() This method was introduced in Python 3. flags – The regular expression flags that will be applied when compiling Let's take an example. " Note: As others pointed out, the new format does not supersede the former, both are available both in Python 3 and the newer versions of Python 2 as well. the same result as if you had called str() on the value. A the precision. Some may say it's a matter of preference, but IMHO the newer is much more expressive than the older, and should be used whenever writing new code (unless it's targeting older environments, of course). With no A primary use case for template strings is for that when fixed-point notation is used to format the from the significand, and the decimal point is also By default, "identifier" is restricted to any IndexError or KeyError should be raised. unicode character before printing. keyword. the same pattern is used both inside and outside braces). internationalization (i18n) since in that context, the simpler syntax and Hex format. Each value type can define its own “formatting In addition, the Formatter defines a number of methods that are The following table shows various ways to format numbers using Python’s str.format(), including examples for both float formatting and integer formatting. It becomes the default when ‘0’ attribute using getattr(), while an expression of the form '[index]' This is a in the C locale: !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~. This value will be passed through in the same place that your placeholder is positioned when you run the program.Let’s print out a string that uses a formatter:In the example above, we construc… The format() method formats the specified value(s) and insert them inside the string's placeholder.. In addition to the above presentation types, integers can be formatted vformat(). subclasses can define their own format string syntax). conversions, trailing zeros are not removed from the result. Converts the value (returned by get_field()) given a conversion type But, is divided into two types of parameters: 1. String of ASCII characters which are considered printable. For integer presentation types 'b', The values can be A number specifying the position of the element you want to If you do this, the value must be a idpattern – This is the regular expression describing the pattern for decimal point, the decimal point is also removed unless A format_spec field can also include nested replacement fields within it. It's far better than earlier % based formatting and template strings. in fixed point, two-decimal format: The format() method formats the specified