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GDScript format strings
Redot offers multiple ways to dynamically change the contents of strings:
Format strings:
var string = "I have %s cats." % "3"The
String.format()method:var string = "I have {} cats.".format([3])String concatenation:
var string = "I have " + str(3) + " cats."
This page explains how to use format strings, and briefly explains the format()
method and string concatenation.
Format strings
Format strings are a way to reuse text templates to succinctly create different but similar strings.
Format strings are just like normal strings, except they contain certain
placeholder character sequences such as %s. These placeholders can then
be replaced by parameters handed to the format string.
Examine this concrete GDScript example:
# Define a format string with placeholder '%s'
var format_string = "We're waiting for %s."
# Using the '%' operator, the placeholder is replaced with the desired value
var actual_string = format_string % "Godot"
print(actual_string)
# Output: "We're waiting for Redot."
Placeholders always start with a %, but the next character or characters,
the format specifier, determines how the given value is converted to a
string.
The %s seen in the example above is the simplest placeholder and works for
most use cases: it converts the value by the same method by which an implicit
String conversion or str() would convert
it. Strings remain unchanged, booleans turn into either "True" or "False",
an int or float becomes a decimal, and other types usually return their data
in a human-readable string.
There are other format specifiers.
Multiple placeholders
Format strings may contain multiple placeholders. In such a case, the values
are handed in the form of an array, one value per placeholder (unless using a
format specifier with *, see dynamic padding):
var format_string = "%s was reluctant to learn %s, but now he enjoys it."
var actual_string = format_string % ["Estragon", "GDScript"]
print(actual_string)
# Output: "Estragon was reluctant to learn GDScript, but now he enjoys it."
Note the values are inserted in order. Remember all placeholders must be replaced at once, so there must be an appropriate number of values.
Format specifiers
There are format specifiers other than s that can be used in placeholders.
They consist of one or more characters. Some of them work by themselves like
s, some appear before other characters, some only work with certain
values or characters.
Placeholder types
One and only one of these must always appear as the last character in a format
specifier. Apart from s, these require certain types of parameters.
|
Simple conversion to String by the same method as implicit String conversion. |
|
A single Unicode character. Expects an unsigned 8-bit integer (0-255) for a code point or a single-character string. |
|
A decimal integer. Expects an integer or a real number (will be floored). |
|
An octal integer. Expects an integer or a real number (will be floored). |
|
A hexadecimal integer with lower-case letters. Expects an integer or a real number (will be floored). |
|
A hexadecimal integer with upper-case letters. Expects an integer or a real number (will be floored). |
|
A decimal real number. Expects an integer or a real number. |
|
A vector. Expects any float or int-based vector object (
|
Placeholder modifiers
These characters appear before the above. Some of them work only under certain conditions.
|
In number specifiers, show + sign if positive. |
Integer |
Set padding. Padded with spaces or with zeroes if integer
starts with |
|
Before |
|
Pad to the right rather than the left. |
|
Dynamic padding, expects additional integer parameter to set
padding or precision after |
Padding
The . (dot), * (asterisk), - (minus sign) and digit
(0-9) characters are used for padding. This allows printing several
values aligned vertically as if in a column, provided a fixed-width font is
used.
To pad a string to a minimum length, add an integer to the specifier:
print("%10d" % 12345)
# output: " 12345"
# 5 leading spaces for a total length of 10
If the integer starts with 0, integer values are padded with zeroes
instead of white space:
print("%010d" % 12345)
# output: "0000012345"
Precision can be specified for real numbers by adding a . (dot) with an
integer following it. With no integer after ., a precision of 0 is used,
rounding to integer values. The integer to use for padding must appear before
the dot.
# Pad to minimum length of 10, round to 3 decimal places
print("%10.3f" % 10000.5555)
# Output: " 10000.556"
# 1 leading space
The - character will cause padding to the right rather than the left,
useful for right text alignment:
print("%-10d" % 12345678)
# Output: "12345678 "
# 2 trailing spaces
Dynamic padding
By using the * (asterisk) character, the padding or precision can be set
without modifying the format string. It is used in place of an integer in the
format specifier. The values for padding and precision are then passed when
formatting:
var format_string = "%*.*f"
# Pad to length of 7, round to 3 decimal places:
print(format_string % [7, 3, 8.8888])
# Output: " 8.889"
# 2 leading spaces
It is still possible to pad with zeroes in integer placeholders by adding 0
before *:
print("%0*d" % [2, 3])
# Output: "03"
Escape sequence
To insert a literal % character into a format string, it must be escaped to
avoid reading it as a placeholder. This is done by doubling the character:
var health = 56
print("Remaining health: %d%%" % health)
# Output: "Remaining health: 56%"
String format method
There is also another way to format text in GDScript, namely the String.format() method. It replaces all occurrences of a key in the string with the corresponding value. The method can handle arrays or dictionaries for the key/value pairs.
Arrays can be used as key, index, or mixed style (see below examples). Order only matters when the index or mixed style of Array is used.
A quick example in GDScript:
# Define a format string
var format_string = "We're waiting for {str}"
# Using the 'format' method, replace the 'str' placeholder
var actual_string = format_string.format({"str": "Godot"})
print(actual_string)
# Output: "We're waiting for Redot"
Format method examples
The following are some examples of how to use the various invocations of the
String.format() method.
Type |
Style |
Example |
Result |
Dictionary |
key |
|
Hi, Godette v3.0! |
Dictionary |
index |
|
Hi, Godette v3.0! |
Dictionary |
mix |
|
Hi, Godette v3.0! |
Array |
key |
|
Hi, Godette v3.0! |
Array |
index |
|
Hi, Godette v3.0! |
Array |
mix |
|
Hi, Godette v3.0! |
Array |
no index |
|
Hi, Godette v3.0! |
Placeholders can also be customized when using String.format, here's some
examples of that functionality.
Type |
Example |
Result |
Infix (default) |
|
Hi, Godette v3.0 |
Postfix |
|
Hi, Godette v3.0 |
Prefix |
|
Hi, Godette v3.0 |
Combining both the String.format method and the % operator could be useful, as
String.format does not have a way to manipulate the representation of numbers.
Example |
Result |
|
Hi, Godette v3.11 |
String concatenation
You can also combine strings by concatenating them together, using the +
operator.
# Define a base string
var base_string = "We're waiting for "
# Concatenate the string
var actual_string = base_string + "Godot"
print(actual_string)
# Output: "We're waiting for Redot"
When using string concatenation, values that are not strings must be converted using
the str() function. There is no way to specify the string format of converted
values.
var name_string = "Godette"
var version = 3.0
var actual_string = "Hi, " + name_string + " v" + str(version) + "!"
print(actual_string)
# Output: "Hi, Godette v3!"
Because of these limitations, format strings or the format() method are often
a better choice. In many cases, string concatenation is also less readable.
Note
In Redot's C++ code, GDScript format strings can be accessed using the
vformat() helper function in the Variant header.