#Klib library python code#The problem with this approach is that this code is fragile to future changes. Worse, the caller might access values inside the returned tuple by index. When the function is evaluated, the results are unpacked into separate names. return 2, False, " blue " > count, enabled, color = f ( ) > tup = f ( ) > enabled = tup Simple function returning a tuple. Let’s look at an example of code that uses plain tuples, to see why such code can be problematic: > def f ( ). The most common situation where a namedtuple is recommended is when a function returns multiple results, which are then unpacked into a tuple. Using namedtuple incurs no extra runtime cost, and can make code much easier to read. The best thing about namedtuple is that you can add it to existing code and use it to progressively replace tuples: it can appear anywhere a tuple is currently being used, without breaking existing code, and without using any extra resources beyond what plain tuples require. color "red" > tup A ( count = 1, enabled = True, color = 'red' ) You get to work with this: > from collections import namedtuple > A = namedtuple ( 'A', 'count enabled color' ) > tup = A ( count = 1, enabled = True, color = "red" ) > tup. The next tool, collections.namedtuple, is magic in a bottle! Instead of working with this: tup = ( 1, True, "red" ) If, instead, you wanted every new element to contain a dictionary, you might say defaultdict(dict). In the preceding examples, we’re saying that every new element, by default, will be an empty list. The setdefault() method of a dict can be used in a somewhat similar way to initialize items with defaults, but defaultdict generally results in clearer code. #Klib library python zip#Here is a simple example of how the ordering changes with a normal dict: > dict ( zip ( ascii_lowercase, range ( 4 ) ) ) for k in keydata : if not k in d : d = d. A mapping is the right solution, and you often need to produce results in the same order in which the input data appeared. A common example is processing lines in a file where the lines (or something within them) maps to other data. The need for an ordered dict comes up surprisingly often. collections.OrderedDictĬollections.OrderedDict gives you a dict that will preserve the order in which items are added to it note that this is not the same as a sorted order. If you’ve been working with Python for any length of time, it is very likely that you have made use of the this module however, the batteries contained within are so important that we’ll go over them anyway, just in case. collectionsįirst up we have the collections module. In this chapter we will mention a few libraries that every Python programmer should know very well. This is understandable because most Python applications deal with input processing however, the Python standard library is very rich and includes a bunch of additional functionality that many Python programmers take too long to discover. The libraries that tend to get all the attention are the ones heavily used for operating-system interaction, like sys, os, shutil, and to a slightly lesser extent, glob. Let’s start by taking a look at the standard library. Rather than focusing on those standouts, this report is instead going to focus on several interesting libraries that are growing in popularity. Many high-quality third-party libraries are already well-known, including Numpy and Scipy, Django, Flask, and Requests you can easily learn more about these libraries by searching for information online. We’re also going to discuss several exciting, lesser-known libraries from the third-party ecosystem. #Klib library python trial#Get a free trial today and find answers on the fly, or master something new and useful. Join the O'Reilly online learning platform.
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