Classifying characters using nested conditional expressions (Python)

2017-04-27T21:26:00-07:00

Python recipe 580792 by Vasudev Ram (characters, classification, conditional_expressions, expressions, join, lambda, map).

Python has a feature called conditional expressions, similar to C's ternary operator. For example:

print n, 'is odd' if n % 2 == 1 else 'is even'

Here, the conditional expression is this part of the print statement above:

'is odd' if n % 2 == 1 else 'is even'

This expression evaluates to 'is odd' if the condition after the if keyword is True, and evaluates to 'is even' otherwise.

The Python Language Reference section for conditional expressions shows that they can be nested. This recipe shows that we can use nested conditional expressions (within a return statement in a user-defined function) to classify characters into lowercase letters, uppercase letters, or neither.

It also shows how to do the same task using map, lambda and string.join, again with a nested conditional expression, but without using return or a user-defined function.

List comparison, difference and more using set & frozenset (Python)

2012-11-01T10:30:58-07:00

Python recipe 578310 by Scott S-Allen (compare, contain, difference, lambda, list, remove, set, union).

Python has a powerful suite of tools for comparing lists by way of sets and frozensets. Here are a few examples and conveniences that many newcomers, even a few seasoned developers, are unaware.

Functional selection sort (Python)

2009-09-29T13:34:35-07:00

Python recipe 576917 by pavel (algorithm, algorithms, functional, lambda, reduce, selection, sort, sorting). Revision 3.

This is a variant of selection sort without using for-statements. Do you like it? :-)

Password Generator (Short Code) (Python)

2011-11-18T03:02:13-08:00

Python recipe 577949 by Alexander James Wallar (alphabet, generator, lambda, password, passwords, password_generator, python, secure, security, short_code). Revision 2.

This recipe generates a pseudo-random password of a prescribed length. It also lets you specify what characters are not permitted in the password or specify what characters are.

lambda program (Python)

2009-07-03T22:03:28-07:00

Python recipe 576829 by nxw (lambda).

An attempt to write a whole program inside a python lambda.

Name a lambda (Python)

2014-07-02T20:54:01-07:00

Python recipe 578902 by David Weil (func_name, introspection, lambda, name, naming).

A very simple recipe to allow you easily name lambda-objects (or other kind of objects, callable, for example, partial objects) you create, with little overhead and friendly syntax.

compare(), making filter() fun again (Python)

2008-10-04T12:40:42-07:00

Python recipe 576526 by Andreas Nilsson (compare, filter, functional, lambda). Revision 2.

compare() takes a function parameter and returns a callable comparator when compared to a value. When called, the comparator returns result of comparing the result of calling the function and the value it was created with.

Basic usage:

items = [1, 2, 3, 4, 5]

def double(x):
    return x * 2

for i in filter(compare(double) > 5, items):
    print i #Prints 3, 4 and 5

Blocks for python (Python)

2011-10-24T22:26:07-07:00

Python recipe 577920 by yoav glazner (block, lambda, python, style).

A simple block function that lets one send multi line blocks of code to a function it doesn't really act like a normal def/lambda but offers cool style

Another use for lambdas and function references (Python)

2009-02-27T06:20:33-08:00

Python recipe 576672 by Kaushik Ghose (function_reference, lambda, loop).

I was writing code to do bootstrapping on a set of data. I wanted a test case where if I asked for one bootstrap I would be returned the original data. lambdas and function references saved me from inefficient code.

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