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Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})
For example, in Python, to print the string Hello, World! followed by a newline, one only needs to write print ("Hello, World!" In contrast, the equivalent code in C++ [ 7 ] requires the import of the input/output (I/O) software library , the manual declaration of an entry point , and the explicit instruction that the output string should be ...
Monty Python references appear frequently in Python code and culture; [190] for example, the metasyntactic variables often used in Python literature are spam and eggs instead of the traditional foo and bar. [190] [191] The official Python documentation also contains various references to Monty Python routines.
The syntax for printing output in Jinja is using the double curly braces, for example {{ Hello, World! }}. Statements which set variables in jinja or those which do not have an output can be wrapped within {% and %}, using the set keyword. For example {% set foo = 42 %} sets a variable called foo with a value of 42.
In this example, /usr/bin/env is the full path of the env command. The environment is not altered. Note that it is possible to specify the interpreter without using env, by giving the full path of the python interpreter. A problem with that approach is that on different computer systems, the exact path may be different.
This example is in Smalltalk, of a typical accessor method to return the value of a variable using lazy initialization. height ^ height ifNil: [ height := 2.0 ] . The 'non-lazy' alternative is to use an initialization method that is run when the object is created and then use a simpler accessor method to fetch the value.
Variables to control the printer. Example: maximum length or maximum depth of expressions to print. Additional command syntax. Some REPLs have commands that follow not the s-expression syntax, but often work with Lisp data as arguments. Graphical REPLs. Some Lisp REPLs (the CLIM Listener is an example) accept also graphical input and output.
The input to eval is not necessarily a string; it may be structured representation of code, such as an abstract syntax tree (like Lisp forms), or of special type such as code (as in Python). The analog for a statement is exec , which executes a string (or code in other format) as if it were a statement; in some languages, such as Python, both ...