# Learning Python as Javascript Developer [Part 1]

This probably will be a series of learning python as a Javascript developer. I can say that I know a few concepts of programming and I have been programming for more than 4 years in different programming languages mostly with JavaScript. 

I will be pointing out things that seem unique to me here in this article except for semicolons. I know we don't need semicolons in python. 

We will be using REPL to learn basic concepts for now. 

## Import 

```bash
➜ python3
Python 3.9.5 (default, May  4 2021, 03:36:27)
[Clang 12.0.0 (clang-1200.0.32.29)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import math
>>> math.sqrt(81)
9.0
>>>
```
Here, We are importing math as the module and the `sqrt` is the attribute inside it, which is basically function. 

## Help 
We may know that `sqrt` belongs to the math module but what about other methods in the math module. We can ask for help with Python REPL for it. 

```
>>> help
Type help() for interactive help, or help(object) for help about the object.
>>>
```

Let's ask for help for the math module. 

```bash
Help on module math:

NAME
    math

DESCRIPTION
    This module provides access to the mathematical functions
    defined by the C standard.

FUNCTIONS
    acos(x, /)
        Return the arc cosine (measured in radians) of x.

        The result is between 0 and pi.

    acosh(x, /)
        Return the inverse hyperbolic cosine of x.

    asin(x, /)
        Return the arc sine (measured in radians) of x.

        The result is between -pi/2 and pi/2.

    asinh(x, /)
        Return the inverse hyperbolic sine of x.

    atan(x, /)
        Return the arc tangent (measured in radians) of x.

        The result is between -pi/2 and pi/2.

    atan2(y, x, /)
        Return the arc tangent (measured in radians) of y/x.

        Unlike atan(y/x), the signs of both x and y are considered.

    atanh(x, /)
        Return the inverse hyperbolic tangent of x.

    ceil(x, /)
        Return the ceiling of x as an Integral.

        This is the smallest integer >= x.

    comb(n, k, /)
        Number of ways to choose k items from n items without repetition and without order.

        Evaluates to n! / (k! * (n - k)!) when k <= n and evaluates
        to zero when k > n.

        Also called the binomial coefficient because it is equivalent
        to the coefficient of k-th term in polynomial expansion of the
:
.....
```

The list is huge, you can scroll down your terminal to find a full list of the functions, properties, and file available on the module. 

```bash
.....

DATA
    e = 2.718281828459045
    inf = inf
    nan = nan
    pi = 3.141592653589793
    tau = 6.283185307179586

FILE
    /usr/local/Cellar/python@3.9/3.9.5/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib-dynload/math.cpython
-39-darwin.so

```

Ok, a few properties seems to be available as properties like:

```bash
>>> math.pi
3.141592653589793
>>> math.inf
inf
>>> math.e
2.718281828459045
>>> math.nan
nan
>>> math.tau
6.283185307179586
>>>
```

You can even ask for help for the specific functions 

```bash
help(math.factorial)


Help on built-in function factorial in module math:

factorial(x, /)
    Find x!.

    Raise a ValueError if x is negative or non-integral.

```

Test it

```bash
>>> math.factorial(5)
120
>>>
```

Let's do more calculation 

```bash
>>> n=5
>>> k=3
>>> math.factorial(n) / (math.factorial(k) * math.factorial(n-k))
10.0
>>>
```

### Different ways of importing modules 

1. We can import the attribute directly from the module 

```bash
>>> from math import factorial
>>> factorial(5)
120
>>>
```

2. We can even rename the attribute imported

```bash
>>> from math import factorial as fac
>>> fac(5)
120
>>>

```

## Division 
```
# / = "Floating division"
# // = "Inter division"

>>> fac(n) / (fac(k) * fac(n-k))
10.0
>>> fac(n) // (fac(k) * fac(n-k))
10
>>>

```

Thank you and to be contained.