Selecting List Elements

Import libraries

>>> import numpy

>>> import numpy as np

Selective import

>>> from math import pi

>>> help(str)

Python For Data Science Cheat Sheet

Python Basics

Learn More Python for Data Science Interactively at www.datacamp.com

Variable Assignment

Strings

>>> x=5

>>> x

5

>>> x+2 Sum of two variables

7

>>> x-2 Subtraction of two variables

3

>>> x*2 Multiplication of two variables

10

>>> x**2 Exponentiation of a variable

25

>>> x%2 Remainder of a variable

1

>>> x/float(2) Division of a variable

2.5

Variables and Data Types

str() '5', '3.45', 'True'

int() 5, 3, 1

float() 5.0, 1.0

bool() True, True, True

Variables to strings

Variables to integers

Variables to floats

Variables to booleans

Lists

>>> a = 'is'

>>> b = 'nice'

>>> my_list = ['my', 'list', a, b]

>>> my_list2 = [[4,5,6,7], [3,4,5,6]]

Subset

>>> my_list[1]

>>> my_list[-3]

Slice

>>> my_list[1:3]

>>> my_list[1:]

>>> my_list[:3]

>>> my_list[:]

Subset Lists of Lists

>>> my_list2[1][0]

>>> my_list2[1][:2]

Also see NumPy Arrays

>>> my_list.index(a)

>>> my_list.count(a)

>>> my_list.append('!')

>>> my_list.remove('!')

>>> del(my_list[0:1])

>>> my_list.reverse()

>>> my_list.extend('!')

>>> my_list.pop(-1)

>>> my_list.insert(0,'!')

>>> my_list.sort()

Get the index of an item

Count an item

Append an item at a time

Remove an item

Remove an item

Reverse the list

Append an item

Remove an item

Insert an item

Sort the list

Index starts at 0

Select item at index 1

Select 3rd last item

Select items at index 1 and 2

Select items after index 0

Select items before index 3

Copy my_list

my_list[list][itemOfList]

Libraries

>>> my_string.upper()

>>> my_string.lower()

>>> my_string.count('w')

>>> my_string.replace('e', 'i')

>>> my_string.strip()

>>> my_string = 'thisStringIsAwesome'

>>> my_string

'thisStringIsAwesome'

Numpy Arrays

>>> my_list = [1, 2, 3, 4]

>>> my_array = np.array(my_list)

>>> my_2darray = np.array([[1,2,3],[4,5,6]])

>>> my_array.shape

>>> np.append(other_array)

>>> np.insert(my_array, 1, 5)

>>> np.delete(my_array,[1])

>>> np.mean(my_array)

>>> np.median(my_array)

>>> my_array.corrcoef()

>>> np.std(my_array)

Asking For Help

>>> my_string[3]

>>> my_string[4:9]

Subset

>>> my_array[1]

2

Slice

>>> my_array[0:2]

array([1, 2])

Subset 2D Numpy arrays

>>> my_2darray[:,0]

array([1, 4])

>>> my_list + my_list

['my', 'list', 'is', 'nice', 'my', 'list', 'is', 'nice']

>>> my_list * 2

['my', 'list', 'is', 'nice', 'my', 'list', 'is', 'nice']

>>> my_list2 > 4

True

>>> my_array > 3

array([False, False, False, True], dtype=bool)

>>> my_array * 2

array([2, 4, 6, 8])

>>> my_array + np.array([5, 6, 7, 8])

array([6, 8, 10, 12])

>>> my_string * 2

'thisStringIsAwesomethisStringIsAwesome'

>>> my_string + 'Innit'

'thisStringIsAwesomeInnit'

>>> 'm' in my_string

True DataCamp

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Scientific computing

Data analysis

2D plotting

Machine learning

Also see Lists

Get the dimensions of the array

Append items to an array

Insert items in an array

Delete items in an array

Mean of the array

Median of the array

Correlation coefficient

Standard deviation

String to uppercase

String to lowercase

Count String elements

Replace String elements

Strip whitespaces

Select item at index 1

Select items at index 0 and 1

my_2darray[rows, columns]

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Calculations With Variables

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Types and Type Conversion

String Operations

List Operations

List Methods

Index starts at 0

String Methods

String Operations

Selecting Numpy Array Elements Index starts at 0

Numpy Array Operations

Numpy Array Functions