Eroman: Created page with "= Advanced control flow = == Task 1 == Make a function that returns the sum of all elements in an iterable >>> my_sum_function([2,3,5]) # 2 + 3 + 5 10..."

2017-03-19T12:24:21Z

Created page with "= Advanced control flow = == Task 1 == Make a function that returns the sum of all elements in an iterable <source lang="python">>>> my_sum_function([2,3,5]) # 2 + 3 + 5 10..."

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= Advanced control flow =

== Task 1 ==

Make a function that returns the sum of all elements in an iterable

<source lang="python">>>> my_sum_function([2,3,5])
# 2 + 3 + 5
10</source>
== all, sum, any ==

<code>all</code>, true if all elements are true<br />
<code>any</code>, true if any elements are true

== Task 2 ==

Find if all elements are false

<source lang="python">opposite_all([False, False])
>>> True</source>
== Task 3 ==

Implement <code>all</code> function with a for loop

<source lang="python">my_all([True, True])
>>> True</source>
== Break loops ==

== Task 4 ==

Implement <code>any</code> with a for loop, use a <code>break</code> statement

== Error Handling ==

* When to raise an exception
* handling user input

=== Example: Addition calculator ===

this calculator is error prone. Users can put in a value that cannot be cast to an integer, which will cause this programs to raise an error.

<source lang="python">def add_two_numbers(a, b):
return int(a) + int(b)

def main():
a = input('Write a number: ')
b = input('Write a number: ')
result = add_two_numbers(a, b)
print(result)

if __name__ == "__main__":
main</source>
giving an error like this on bad user input

<pre>Write a number: a
Write a number: 1
Traceback (most recent call last):
File "calc.py", line 12, in <module>
main()
File "calc.py", line 7, in main
result = add_two_numbers(a, b)
File "calc.py", line 2, in add_two_numbers
return int(a) + int(b)
ValueError: invalid literal for int() with base 10: 'a'
</pre>
==== With error handled ====

<source lang="python">def add_two_numbers(a, b):
return int(a) + int(b)

def main():
a = input('Write a number: ')
b = input('Write a number: ')
try:
result = add_two_numbers(a, b)
except ValueError:
print('you must type a valid integer!')
else:
print(result)

if __name__ == "__main__":
main()</source>
==== With checking before ====

<source lang="python">def add_two_numbers(a, b):
return int(a) + int(b)

def main():
a = input('Write a number: ')
b = input('Write a number: ')
if a.isdigit() and b.isdigit():
result = add_two_numbers(a, b)
print(result)
else:
print('you must type a valid integer!')

if __name__ == "__main__":
main()</source>
= Splats =

* dict as kwargs
* list as args

== Task: Sum of all arguments ==

=== Solution ===

<source lang="python">def sum_args(*args):
return sum(args)

if __name__ == "__main__":
print(sum_args(1, 3, 5)) # 9
</source>
=== Pass a list into the function ===

<source lang="python">def sum_args(*args):
return sum(args)

if __name__ == "__main__":
print(sum_args(*[1, 3, 5])) # 9
</source>

I719 Fundamentals of Python/lecture7 - Revision history

Eroman: Created page with "= Advanced control flow = == Task 1 == Make a function that returns the sum of all elements in an iterable >>> my_sum_function([2,3,5]) # 2 + 3 + 5 10..."