Monthly Archives: December 2017

How to sort a dictionary by values in Python

Tweet By definition, dictionary are not sorted (to speed up access). Let us consider the following dictionary, which stores the age of several persons as values:

If you want to sort this dictionary by values (i.e., the age), you … Continue reading

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Python: how to copy a list

Tweet To explain how to create a copy of a list, let us first create a list. We will use a simple list of 4 items:

Why do we want to create a copy anyway ? Well, because in … Continue reading

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Python: ternary operator

Tweet In C language (and many other languages), there is a compact ternary conditional operator that is a compact if-else conditional construct. For instance, in C, a traditional if-else construct looks like:

and the equivalent ternary operator looks like: … Continue reading

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Difference between __repr__ and __str__ in Python

Tweet When implementing a class in Python, you usually implement the __repr__ and __str__ methods. __str__ should print a readable message __repr__ should print a message that is unambigous (e.g. name of an identifier, class name, etc). You can see … Continue reading

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python: how to merge two dictionaries

Tweet Let us suppose two dictionaries storing ages of different individuals:

If you do mind losing the contents of either list1 or list2 variable, you can update one of the other as follows:

Now list1 variable contains:

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Search for a pattern in a set of files using find and grep commands

Tweet A common task for developers is to search for a pattern amongst a bunch of files that are in different directories. For instance, you are looking for the pattern “import sys” within a set of Python files. Those files … Continue reading

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