Key takeaways:
The
Templateclass in Python supports two substitution methods:substitute()andsafe_substitute().
substitute(): Replaces placeholders but raises aKeyErrorif any placeholder is missing.
safe_substitute(): Handles missing placeholders gracefully by leaving them unchanged.Templates are versatile tools for generating customized outputs, such as HTML web reports, plain text, and XML files, simplifying the development process across various formats.
Python's string templates provide a simpler and safer alternative to traditional string formatting methods, enhancing code readability and preventing errors when dealing with user-provided input.
Templates are used to represent data in different forms. In particular, web templates are more attractive and readable for users. Templating usually involves a document (the template itself) and defined data.
Templates serve as a blueprint for generating dynamic content. The combination of templates and data produces the final output. However, they contain placeholders instead of actual data that can act as variables. One of the simplest forms is used to substitute values into a template in order to produce the final output (commonly known as String Templates).
A string template in Python is a way to perform string substitution using the Template class from the string module. It provides an alternative to the traditional string formatting methods (% formatting, .format(), and f-strings) by using a simpler and safer substitution mechanism, especially useful in scenarios requiring user-provided input.
substitute methodssubstitute(mapping, **kwds):
Performs substitutions where placeholders are replaced by corresponding values from a dictionary or keyword arguments.
Raises a KeyError if any placeholder key is missing.
safe_substitute(mapping, **kwds):
Similar to substitute, but does not raise a KeyError for missing keys; instead, it leaves the placeholder as is.
To create a string template in Python, you use the Template class from the string module. A string template is initialized with a string containing placeholders in the format $variable_name or ${variable_name}.
Import the Template class from the string module.
Define a template string with placeholders.
Use .substitute() or .safe_substitute() to replace placeholders with values.
substitute()Here, we’ll dive into the substitute method using the code example given below.
# A Python program to demonstrate working of string templatefrom string import Template# We are creating a basic structure to print the name and# marks of the students.t = Template('Hi $name, you got $marks marks on the Math Exam')#for i in Student:print (t.substitute(name = 'Alex', marks = 56))
In the code, the class template allows us to create simplified syntax using placeholder identifiers formed by name and marks. The values for the placeholders are passed as a parameter in the substitute() function, which results in the final output.
One key application for templates is differentiating program logic from the details of multiple output formats. This makes using custom templates for XML files, plain text reports, and HTML web reports feasible.
safe_substitute() to handle missing variablesIf a variable is missing in .substitute(), it raises a KeyError. To avoid this, use .safe_substitute().
from string import Templatetemplate = Template("Hello, $name! Your balance is $balance.")# Using safe_substitute() to avoid errors if variables are missingresult = template.safe_substitute(name="Bob")print(result) # $balance remains unchanged
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String templates in Python simplify generating dynamic outputs while separating program logic from output formats. Using the string.Template class with methods like substitute() and safe_substitute(), developers can create customizable web pages, reports, and XML files efficiently. These templates enhance readability, maintainability, and development efficiency across various applications.
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