Numpy Basic-1

Basics of Numpy. How to create a numpy array¶

Data manipulation with Numpy¶

In [2]:

import numpy as np

In [2]:

a=np.array([1,2,3])
a

Out[2]:

array([1, 2, 3])

In [3]:

a[0]

Out[3]:

1

In [4]:

a[2]

Out[4]:

3

Let's compare Numpy array vs Python list¶

In [3]:

import time
import sys

Size comp¶

In [7]:

b=range(1000)
print(sys.getsizeof(b)*len(b))

48000

In [9]:

c=np.arange(1000)
print(c.size*c.itemsize)

4000

Speed comp¶

In [4]:

size=100000
L1=range(size)
L2=range(size)
A1=np.arange(size)
A2=np.arange(size)

In [5]:

start=time.time()
result=[(x+y) for x,y in zip(L1,L2)]
print("python list took:",(time.time()-start)*1000)

python list took: 24.99556541442871

In [6]:

start=time.time()
result=A1+A2#Convinient
print("Numpy array took:",(time.time()-start)*1000)

Numpy array took: 8.643150329589844

In [16]:

a=np.array([[1,2],[3,4],[5,6]])
a

Out[16]:

array([[1, 2],
       [3, 4],
       [5, 6]])

In [17]:

a.ndim

Out[17]:

2

In [18]:

a.itemsize

Out[18]:

4

In [19]:

a.shape

Out[19]:

(3, 2)

In [20]:

a=np.array([[1,2],[3,4],[5,6]],dtype=np.float64)
a

Out[20]:

array([[1., 2.],
       [3., 4.],
       [5., 6.]])

In [21]:

a.itemsize

Out[21]:

8

In [22]:

a.shape

Out[22]:

(3, 2)

In [23]:

a=np.array([[1,2],[3,4],[5,6]],dtype=np.complex)
a

Out[23]:

array([[1.+0.j, 2.+0.j],
       [3.+0.j, 4.+0.j],
       [5.+0.j, 6.+0.j]])

In [24]:

np.zeros((3,4))

Out[24]:

array([[0., 0., 0., 0.],
       [0., 0., 0., 0.],
       [0., 0., 0., 0.]])

In [25]:

np.ones((3,4))

Out[25]:

array([[1., 1., 1., 1.],
       [1., 1., 1., 1.],
       [1., 1., 1., 1.]])

In [26]:

l=range(5)
l

Out[26]:

range(0, 5)

In [27]:

np.arange(5)

Out[27]:

array([0, 1, 2, 3, 4])

In [28]:

print('Concat Ex:')
print(np.char.add(['hello','hi'],['abc','xy']))

Concat Ex:
['helloabc' 'hixy']

In [29]:

print(np.char.multiply('hello',3))

hellohellohello

In [30]:

print(np.char.center('hello',29,fillchar='*'))

************hello************

In [31]:

print(np.char.capitalize('hello'))

Hello

In [32]:

print(np.char.title('hello, how are you?'))

Hello, How Are You?

In [33]:

print(np.char.lower('hello, how are you?'))
print(np.char.upper('hello, how are you?'))

hello, how are you?
HELLO, HOW ARE YOU?

In [34]:

print(np.char.split('hello, how are you?'))

['hello,', 'how', 'are', 'you?']

In [36]:

print(np.char.splitlines('hello\n how are you?'))

['hello', ' how are you?']

In [37]:

print(np.char.strip(['nina','Shakti','Sampada'],'a'))

['nin' 'Shakti' 'Sampad']

In [38]:

print(np.char.join([':','-'],['20190101','20190201']))

['2:0:1:9:0:1:0:1' '2-0-1-9-0-2-0-1']

In [39]:

print(np.char.replace('Hi How are you?','Hi','Hi,'))

Hi, How are you?

In [ ]: