\documentclass[14pt,compress,aspectratio=169]{beamer}

\input{macros.tex}

\title[Practice advanced functions]{Advanced Python}
\subtitle{Practice advanced functions}

\author[FOSSEE] {The FOSSEE Group}

\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
\date[] {Mumbai, India}

\begin{document}

\begin{frame}
  \titlepage
\end{frame}

\begin{frame}[plain, fragile]
  \frametitle{Exercise: product of all arguments}
  \begin{block}{}
    Write a function called \lstinline{prod} that can be called with any
    number of arguments (at least one) but computes the product of all the
    given values as seen below.
  \end{block}

\begin{lstlisting}
In []: prod(2.,  2.)
Out[]: 4.0

In []: prod(1, 2, 3)
Out[]: 6
\end{lstlisting}
\end{frame}

\begin{frame}[plain, fragile]
  \frametitle{Solution}
\begin{lstlisting}
def prod(*args):
    res = 1.0
    for x in args:
        res *= x
    return res

\end{lstlisting}
\end{frame}

\begin{frame}[plain, fragile]
  \frametitle{Another solution}
\begin{lstlisting}
def prod(*args):
    res = args[0]
    for i in range(1, len(args)):
        res *= args[i]
    return res

\end{lstlisting}
\end{frame}


\begin{frame}[plain, fragile]
  \frametitle{Exercise: function applied to arguments}
  \begin{block}{}
    Write a function called \lstinline{apply} which takes a function followed
    by an arbitrary number of arguments and returns a list with the function
    applied to all the arguments as shown below.
  \end{block}

\begin{lstlisting}
In []: def twice(x):
  ...:     return x*2

In []: apply(twice,  1, 2)
Out[]: [2, 4]

In []: apply(twice,  1, 2, 3)
Out[]: [2, 4, 6]

\end{lstlisting}
\end{frame}


\begin{frame}[plain, fragile]
  \frametitle{Solution}
\begin{lstlisting}
def apply(f, *args):
    result = []
    for arg in args:
        result.append(f(arg))
    return result
\end{lstlisting}
\end{frame}

\begin{frame}[plain, fragile]
  \frametitle{Exercise: number of kwargs}
  \begin{block}{}
    Write a function \lstinline{nkw} that takes an arbitrary number of
    keyword arguments and returns the number of keyword arguments passed.
  \end{block}

\begin{lstlisting}
In []: nkw(x=1, y=2)
Out[]: 2

In []: nkw()
Out[]: 0

In []: nkw(x=1)
Out[]: 1
\end{lstlisting}
\end{frame}


\begin{frame}[plain, fragile]
  \frametitle{Solution}
\begin{lstlisting}
def nkw(**kw):
    return len(kw)
\end{lstlisting}
\end{frame}

\begin{frame}[plain, fragile]
  \frametitle{Exercise: name of kwargs}
  \begin{block}{}
    Write a function \lstinline{kwname} that takes an arbitrary number of
    keyword arguments and returns a sorted list of the keyword arguments
    passed.
  \end{block}

\begin{lstlisting}
In []: kwname(x=1, y=2)
Out[]: ['x', 'y']

In []: kwname()
Out[]: []

In []: kwname(z=1, a=2)
Out[]: ['a', 'z']
\end{lstlisting}
\end{frame}


\begin{frame}[plain, fragile]
  \frametitle{Solution}
\begin{lstlisting}
def kwname(**kw):
    return sorted(kw.keys())
\end{lstlisting}
\end{frame}

\begin{frame}[plain, fragile]
  \frametitle{Exercise: power function}
  \begin{block}{}
    Write a function called \lstinline{power} that is given a single integer
    and returns a function that takes a single number but returns its power.
    For example:
  \end{block}

\begin{lstlisting}
In []: pow2 = power(2)
In []: pow2(2)
Out[]: 4
In []: pow2(4)
Out[]: 16

In []: pow3 = power(3)
In []: pow3(2)
Out[]: 8
\end{lstlisting}
  Hint: this is a closure.
\end{frame}


\begin{frame}[plain, fragile]
  \frametitle{Solution}
\begin{lstlisting}
def power(n):
    def g(x):
        return x**n
    return g

\end{lstlisting}
\end{frame}


\begin{frame}[plain, fragile]
  \frametitle{Exercise: debug function}
  \begin{block}{}
    Write a function called \lstinline{debug} that takes any function as a
    single positional argument but returns a function that first prints out
    the arguments passed to the function before calling it and returning its
    value. For example:
  \end{block}

\begin{lstlisting}
In []: debug(max)(1, 2)
(1, 2) {}
Out[]: 2

In []: import math

In []: debug(math.sin)(1.0)
(1.0,) {}
Out[]: 0.8414709848078965

\end{lstlisting}
\end{frame}


\begin{frame}[plain, fragile]
  \frametitle{Solution}
\begin{lstlisting}
def debug(f):
    def g(*args, **kw):
        print(args, kw)
        return f(*args, **kw)
    return g
\end{lstlisting}
\end{frame}


\end{document}