Identifiers An identifier is a name given to entities like variables,functions,class, functions etc. It helps to differentiate one entity from another. Rules for writing identifiers 1.Identifiers can be a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore _. Names like myClass, var_1 and print_this_to_screen, all are valid example. 2.An identifier cannot start with a digit. 1variable is invalid, but variable1 is a valid name. 3.Keywords cannot be used as identifiers. Eg: global = 1 is invalid 4.We cannot use special symbols like !, @, #, $, % etc. in our identifier. a@=0 is invalid 5.An identifier can be of any length. Things to Remember Python is a case-sensitive language. This means, Variable and variable are not the same. Always give the identifiers a name that makes sense. While c = 10 is a valid name, writing count=10 would make more sense, and it would be easier to figure out what it represents when you look at your code after
NumPy (Numerical Python)is a library for the Python programming language, adding support for large, multi-dimensional arrays and matrices , along with a large collection of high-level mathematical functions to operate on these arrays. The ancestor of NumPy, Numeric, was originally created by Jim Hugunin with contributions from several other developers. In 2005, Travis Oliphant created NumPy by incorporating features of the competing Numarray into Numeric, with extensive modifications. NumPy is open-source software and has many contributors. To use the numpy package in your program, you have to import the package as follows import numpy as np Arrays A numpy array is a grid of values, all of the same type, and is indexed by a tuple of non negative integers. In NumPy dimensions are called axes.The number of dimensions is the rank of the array; the shape of an array is a tuple of integers giving the size of the array along each dimension. We can initialize numpy arrays