first steps into loops

Author: thomasWeise

styles/listing.sty

@@ -272,13 +272,20 @@ $\downarrow$~~\expandafter\bashil{python3 #3}~~$\downarrow$%
 %
 %%
 %% The python syntax environment.
+%% Warning: If we do not use the minipage, this may or may not
+%% cause strange errors like:
+%% "! Argument of ? has an extra }."
 \lstnewenvironment{pythonSyntax}[1][true]{%
+\center%
+\minipage{\linewidth}%
 \let\@old@lst@visiblespace\lst@visiblespace%
 \def\lst@visiblespace{{\color{Gray}\@old@lst@visiblespace}}%
 \lstset{%
 style=python_style,%
 showspaces=#1%
 }}{%
 \let\lst@visiblespace\@old@lst@visiblespace%
+\endminipage%
+\endcenter%
 }%
 %

styles/myindex.sty

@@ -9,6 +9,7 @@
 %
 \protected\gdef\pythonIdx#1{\index[python]{#1}}%
 \protected\gdef\pythonilIdx#1{\index[python]{#1}\pythonil{#1}}%
+\protected\gdef\pythonilsIdx#1{\index[python]{#1}\pythonils{#1}}%
 \makeindex%
 %
 %% dots without end-of-sentence spacing at the end

text/main/basics/collections/lists/lists.tex

@@ -5,6 +5,7 @@
 They work very similar to the strings we already discussed in \cref{sec:str}, but instead of characters, they can contain any kind of objects and they can be modified.%
 %
 \hsection{Basic Functionality and Examples}%
+\label{sec:lists:basicFunctions}%
 %
 \gitPythonAndOutput{\programmingWithPythonCodeRepo}{02_collections}{lists_1.py}{--args format}{lists:lists_1}{%
 A first example for using lists in \python: creating, indexing, printing of and appending elements and other lists to lists.}%
@@ -103,7 +104,7 @@
 \pythonil{[5, 6, 7] * 3}\pythonIdx{*}\pythonIdx{list!*} therefore yields \pythonil{[5, 6, 7, 5, 6, 7, 5, 6, 7]}.
 
 In \cref{sec:strBasicOperations}, we discussed string slicing.
-Lists can be sliced in pretty much the same way\pythonIdx{list!slicing}\pythonIdx{slicing}~\cite{PSF2024S}.
+Lists can be sliced in pretty much the same way\pythonIdx{list!slicing}\pythonIdx{slicing}\pythonIdx{slice}~\cite{PSF2024S}.
 When slicing a list~\pythonil{l} or a string, you can provide either two or three values in the square brackets\pythonIdx{[\idxdots]}\pythonIdx{[i:j:k]}, i.e., either do~\pythonil{l[i:j]}\pythonIdx{[i:j]}\pythonIdx{slicing} or \pythonil{l[i:j:k]}.
 If \pythonil{j < 0}, then it is replaced with~\pythonil{len(l) - j}.
 In both the two and three indices case, \pythonil{i} is the inclusive start index and \pythonil{j} is the exclusive end index, i.e., all elements with index~\pythonil{m} such that \pythonil{i <= m < j}.
@@ -122,7 +123,7 @@
 It stops adding elements before reaching index~\pythonil{3}.
 Therefore, the result will be the new list~\pythonil{l7 = [7, 5, 6]}.
 
-Notice that the slices we create are independent copies of ranges of the original lists.
+Notice that the slices\pythonIdx{slice} we create are independent copies of ranges of the original lists.
 The list~\pythonil{l7} is a slice from the list~\pythonil{l4}.
 If we modify it, e.g., set \pythonil{l7[1] = 12}, then we set the second element of~\pythonil{l7} to~\pythonil{12}.
 \pythonil{l7}~becomes~\pythonil{[7, 12, 6]}.

text/main/basics/simpleDataTypesAndOperations/str/str.tex

@@ -60,8 +60,8 @@
 Of course, using a negative index that would bring us out of the string's valid range, such as \pythonil{-6}, again yields an \pythonilIdx{IndexError}.
 
 We can also obtain whole substrings by using index ranges, where the inclusive starting index and the \emph{exclusive} end index are separated by a~\pythonilIdx{:}.
-In other words, applying the index \pythonil{[a:b]}\pythonIdx{[i:j]}\pythonIdx{slicing} to a string results in all characters in the index range from \pythonil{a} to \pythonil{b - 1}.
-Doing this is called \emph{string slicing}\pythonIdx{str!slicing}\pythonIdx{slicing}.
+In other words, applying the index \pythonil{[a:b]}\pythonIdx{[i:j]}\pythonIdx{slicing}\pythonIdx{slice} to a string results in all characters in the index range from \pythonil{a} to \pythonil{b - 1}.
+Doing this is called \emph{string slicing}\pythonIdx{str!slicing}\pythonIdx{slicing}\pythonIdx{slice}.
 \pythonil{"Hello"[0:3]} yields a string composed of the characters at positions~0, 1, and~2 inside \pythonil{"Hello"}, i.e., \pythonil{"Hel"}.
 The end index is always excluded, so the character at index~3 is not part of the result.
 If we do \pythonil{"Hello"[1:3]}, we get \pythonil{"He"}, because only the characters at indices~1 and~2 are included.

text/main/controlFlow/conditionals/conditionals.tex

@@ -1,8 +1,10 @@
 \hsection{Conditional Statements}%
 %
+Conditional statements allow us to execute a piece of code if a certain Boolean expression evaluates to~\pythonilIdx{True}.
+This allows us to let the program make choices, to do one thing in one situation and another thing in a different situation.
+Conditionals are therefore the most fundamental control flow statement.%
+%
 \hsection{The \texttt{if} Statement}%
-\gitPythonAndOutput{\programmingWithPythonCodeRepo}{03_conditionals}{if_example.py}{--args format}{conditionals:if}{%
-An example for using the \pythonilIdx{if} statement.}%
 %
 A conditional statement is basically a piece of program code which will execute a set of instructions if a condition is met.
 The condition is provided as the kind of Boolean expressions that we already discussed back in \cref{sec:bool}.
@@ -19,6 +21,10 @@
 # ...
 \end{pythonSyntax}
 %
+\FloatBarrier%
+\gitPythonAndOutput{\programmingWithPythonCodeRepo}{03_conditionals}{if_example.py}{--args format}{conditionals:if}{%
+An example for using the \pythonilIdx{if} statement.}%
+%
 The first line begins with \pythonilIdx{if}~statement, followed by a Boolean expression, followed by a colon~(\pythonilIdx{:}).
 If -- and only if -- the Boolean expression evaluates to~\pythonilIdx{True}, then the \emph{indented} block of statements below the \pythonil{if} are executed.
 Notice that each of these conditionally executed statements is indented by four spaces compared to the~\pythonil{if}.
@@ -142,12 +148,12 @@
 In some cases, we need to query a sequence of alternatives in such a way that \pythonilIdx{else}~blocks would be nested over \pythonilIdx{else}~blocks over \pythonilIdx{else}~blocks, and so on.
 Since everytime we nest a conditional statement into another one we have to add four spaces of indentation, this would quickly fill the horizontal of our screens and look rather ugly.
 Therefore, the \pythonilIdx{elif} statement has been developed, which can replace an \pythonil{else} containing just another \pythonil{if}.
-The syntax of a combined \pythonil{if ... elilf} looks like this:%
+The syntax of a combined \pythonil{if ... elif} looks like this:%
 %
 \begin{pythonSyntax}
 if booleanExpression 1:
     conditional 1 statement 1
-    conditional 2 statement 2
+    conditional 1 statement 2
     # ...
 elif booleanExpression 2:  # such block can be placed arbitrarily often
     conditional 2 statement 1

text/main/controlFlow/controlFlow.tex

@@ -9,6 +9,7 @@
 Now you will learn how to write programs that \emph{do} branch or loop.%
 %
 \hinput{conditionals}{conditionals.tex}%
+\hinput{loops}{loops.tex}%
 %
 \endhsection%
 %

text/main/controlFlow/loops/loops.tex

@@ -0,0 +1,57 @@
+\hsection{Loops}%
+%
+When we are working with sequences of data, we do not just want to perform an action on one data element.
+We instead often want to apply the actions repetitively to all data elements.
+Loops allow us to do just that, to perform the same actions multiple times.%
+\pythonIdx{loop}%
+%
+\hsection{The \texttt{for} Loop Statement}%
+%
+\pythonIdx{loop!for}%
+The most basic such sequence in \python\ may be the \pythonilIdx{for}~loop, which has the following pattern:%
+%
+\begin{pythonSyntax}
+for loopVariable in sequence:
+    loop body statement 1
+    loop body statement 2
+    # ...
+
+normal statement 1
+normal statement 2
+# ...
+\end{pythonSyntax}
+%
+%
+\gitPythonAndOutput{\programmingWithPythonCodeRepo}{04_loops}{for_loop_range.py}{--args format}{loops:for_loop_range}{%
+An example for using the \pythonilIdx{for} loop over a \pythonilsIdx{range} of integer numbers.}%
+%
+\gitPythonAndOutput{\programmingWithPythonCodeRepo}{04_loops}{for_loop_pi_liu_hui.py}{--args format}{loops:for_loop_pi_liu_hui}{%
+A variant of \cref{lst:variables:pi_liu_hui} which uses a \pythonilIdx{for} loop instead of five copies of the same instructions.}%
+%
+\gitPythonAndOutput{\programmingWithPythonCodeRepo}{04_loops}{for_loop_continue_break.py}{--args format}{loops:for_loop_continue_break}{%
+An example for the \pythonilIdx{continue} and \pythonilIdx{break} statements in a \pythonilIdx{for} loop.}%
+%
+The keyword~\pythonilIdx{for} is followed by a loop variable.
+Then comes the keyword~\pythonilIdx{in}, the \pythonil{sequence} we want to iterate over, and finally a colon~(\pythonilIdx{:}).
+This variable will iteratively take on the values in the \pythonil{sequence}.
+The loop body statements in the following, indented block are executed for each of these values.
+After the loop, we leave a blank line followed by the code that will be executed after the loop completes.
+
+In its most simple form, the \pythonilIdx{for} loop is applied to a \pythonilIdx{range} of integer numbers.
+Ranges are sequences which work basically like slices\pythonIdx{slice} (see \cref{sec:lists:basicFunctions,sec:strBasicOperations}).
+\pythonil{range(5)} will give us a sequence of integers starting with~0 and reaching up to right \emph{before}~5, i.e., the integer range~\intRange{0}{4}.
+\pythonil{range(6, 9)} gives the sequence of integers starting with~6 and stopping right \emph{before}~9, i.e., the integer range~\intRange{6}{8}.
+Finally, \pythonil{range(20, 27, 2)} results in a sequence of integers that begins at~20, increments by~2 in each step, and ends right before~27.
+This is the sequence~$(20, 22, 24, 26)$.
+\pythonilsIdx{range}, like slices\pythonIdx{slice}, can also have negative increments:
+The \pythonil{range(40, 30, -3)} starts with~40 and stops before reaching~30 and decrements by~3 in each step.
+This is equivalent to the set~$(40, 37, 34, 31)$.
+
+In \cref{lst:loops:for_loop_range}, we loop over exactly these ranges.
+In this listing, we try to create a dictionary (see \cref{sec:dictionaries}) where some integer numbers are mapped to their squares.
+We use four \pythonilIdx{for} loops to fill this dictionary with data.%
+%
+\endhsection%
+%
+\endhsection%
+%