added multiple assignments and variable swapping

Author: thomasWeise

text/back/backmatter.tex

@@ -9,7 +9,6 @@
 \checkandfixthelayout%
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 \printBestPractices%
-\printacronyms%
 \printglossaries%
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 \renewcommand{\indexname}{Index of \python\ Commands}%

text/main/basics/variables/assignment/assignment.tex

@@ -108,7 +108,7 @@
 This program does not do anything useful, but it illustrates how variables can be used.
 
 It begins by assigning the \pythonilIdx{int} value~\pythonil{1} to a variable named~\pythonil{int_var}.
-We could have chosen any other name as well, as long as it does not contain spaces, e.g., \pythonil{myvalue}, \pythonil{cow}, \pythonil{race_car}.
+We could have chosen any other name as well, as long as it does not contain spaces, e.g., \pythonil{my_value}, \pythonil{cow}, \pythonil{race_car}.
 But we chose \pythonil{int_var}.
 The \pythonilIdx{=} assigns the value~\pythonil{1} to \pythonil{int_value}.
 As \cref{fig:variable:assignment1} illustrates, the value~\pythonil{1} will now be stored somewhere in memory and \pythonil{int_var} is a name that points to this memory location.%
@@ -290,5 +290,6 @@
 %
 \endhsection%
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+\FloatBarrier%
 \endhsection%
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text/main/basics/variables/multiAndSwap/multiAndSwap.tex

@@ -0,0 +1,29 @@
+\hsection{Multiple Assignments and Value Swapping}%
+%
+\gitPythonAndOutput{\programmingWithPythonCodeRepo}{01_variables}{multi_and_swap.py}{--args format}{variables:multi_and_swap}{%
+A \python\ program assigning multiple values to multiple variables and using the same method to swap variable values.}%
+%
+In \python, we can assign values to multiple variables at once.
+In this case, we separate both the variable names and the values with commas.
+The first line (\pythonil{a, b = 5, 10}\pythonIdx{=!multiple}\pythonIdx{,}) in \cref{lst:variables:multi_and_swap} assigns the values~\pythonil{5} and~\pythonil{10}, respectively, to the variables~\pythonil{a} and~\pythonil{b}, respectively.
+After this assignment step, \pythonil{a == 5} and \pythonil{b == 10} holds.
+\pythonil{print(f"a={a}, b={b}")} therefore prints \textit{a=5, b=10}.
+
+This method can also be used to \emph{swap} the values of two variables\pythonIdx{=!swap}\pythonIdx{swap}.
+Writing \pythonil{a, b = b, a} looks a bit strange but it basically means \inQuotes{the \emph{new} value of \pythonil{a} will be the \emph{present} value of \pythonil{b} and the \emph{new} value of \pythonil{b} will be the \emph{present} value of \pythonil{a}.}
+The line is therefore basically equivalent to first storing~\pythonil{a} in a temporary variable~\pythonil{t}, then overwriting \pythonil{a} with \pythonil{b}, and finally copying the value of \pythonil{t} to \pythonil{t}.
+But it accomplishes this in single line of code instead of three.
+\pythonil{print(f"a={a}, b={b}")} thus now prints \textit{a=10, b=5}.%
+%
+\bestPractice{swap}{Swapping of variable values can best be done with a multi-assignment statement, e.g., \pythonil{a, b = b, a}\pythonIdx{=!swap}\pythonIdx{swap}.}%
+%
+The same concept of multiple assignments works for arbitrarily many variables.
+\pythonil{z, y, x = 1, 2, 3} assigns, respectively, \pythonil{1} to \pythonil{z}, \pythonil{2} to \pythonil{y}, and \pythonil{3} to \pythonil{x}.
+\pythonil{print(f"x={x}, y={y}, z={z}")} thus yields \textil{x=3, y=2, z=1}.
+
+We can also swap multiple values.
+\pythonil{x, y, z = z, y, x} assigns the present value of \pythonil{z} to become the new value of \pythonil{x}, the present value of \pythonil{y} to also be the new value of \pythonil{y}, and the present value of \pythonil{x} to become the new value of \pythonil{z}.
+\pythonil{print(f"x={x}, y={y}, z={z}")} now gives us \textil{x=1, y=2, z=3}.
+%
+\endhsection%
+%

text/main/basics/variables/variables.tex

@@ -8,6 +8,7 @@
 For this purpose, variables exist.%
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 \hinput{assignment}{assignment.tex}%
+\hinput{multiAndSwap}{multiAndSwap.tex}%
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 \endhsection%
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