Python cookbook

Iterate Python dictionary (associative arrays) Using keys It is not memory efficient for large dictionaries. Using values It is not memory efficient for large dictionaries. read more

Python cloning an array (list) using slice operator.

To merge two (or more) lists (arrays) the operator plus (+) can be used. It will append items of 2nd list to first list and read more

Python string can be converted to int using int(strval). Note that it will throw ValueError for invalid string. Here is a quick example to convert read more

Python int (or any other data type like float) needs to be converted to string before we can do concatenation operation using plus (+). It read more

Python dictionary (associative arrays) – some basic operations. Initialize dictionary Check if a key exists access value for a key list length/size using len() len() read more

To initialize a large list with same value (all items having same value), the following syntax can be used. a = [val] * num_items Example

Slicing a list (array) in python is very handy way to get a sub list of an array. Its syntax is ## slice from start read more

To remove an item from python list method pop([i]) can be used. Remove last item Remove first item Remove ith item

Appending or prepending a value to a list in Python. Append value Prepend value

Python list (or array) – some basic operations. Initialize list access ith item access last item list length/size using len() Note than len() can also read more

To check if a string is part of another string (case sensitive) we can use these approaches Using in operator Using string find() method ## read more

To convert a string to lowercase of uppercase following code can be used: s_lower = s.lower() s_upper = s.upper() string lowercase example string uppercase example

Python if else statements can be expressed on two ways Simple if-else statement if-elif-else statement with one or more occurrences of elif. if else example read more

Python elt library petl can be used to perform extract/load – reading/writing tables from files and databases. In this tutorial we’ll read a table in read more

Reading and writing files in python is very common use case. Here are some examples: Write to file using “with open()” Here file gets closed read more

In Python we frequently need to check if a value is in an array (list) or not. Python x in list can be used for read more

Python has in-built string split function which can be used to split a string on any delimiter and return a python list (array). If no read more

Python built-in data type string is very frequently used in any python program. Here are some examples of using strings to get started with. Print read more

Get dictionary key with default if not found using method get() This is better approach in most cases. Get dictionary key using square brackets ([]) read more

Frequently used python for loop examples. For loop to iterate over a list Iterate on each element of a list Iterate on each index, element read more

Here is simple python code snippet to see the file location of a python package on command line: $ python -c “import urllib2; print urllib2.__file__;” read more

Sometime we need to run a quick static webserver which can serve various files in a directory. This can be pretty handy to serve html read more

Sometimes we want to iterate over a dictionary in sorted order of values. We can do it by using key argument to python sorted() method read more