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Lesson 6: Data Conversion Recipes

Pragmatic AI Labs

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6.1 Convert lists to dicts, and dicts to lists

Converting Lists to Dictionaries

Create basic dictionary

key_values = [('one', 1), ('two', 2), ('three', 3)]
d = dict( key_values )
d

{'one': 1, 'three': 3, 'two': 2}

Zip two lists

instruments = [ 'violin', 'lute', 'banjo', 'accordian']
players = [ 'Anne-Sophie Mutter', 'Julian Bream', 'Noam Pikelny', 'Astor Pantaleón Piazzolla']

d = dict(zip(instruments, players))
d

From keys

racers = ['Tom', 'Bill', 'Will', 'Jill']
start_distance = 0
d = dict.fromkeys(racers, start_distance)
d

Converting Dictionaries to Lists

d = {'name': 'toby', 'id' : 14}

Get a list of keys

list(d)

Get keys in sorted order

sorted(d)

Get list of values

list(d.values())

6.2 Convert dicts to pandas Dataframe

Create DataFrame using data parameter

from pandas import DataFrame

d = {'first': ['Jill', 'Solma', 'Elizabeth'], 'last': ['Stein', 'Smith', 'Tudor']}
DataFrame(data=d)
first last
0 Jill Stein
1 Solma Smith
2 Elizabeth Tudor

Use class from_dict method

DataFrame.from_dict(d)
first last
0 Jill Stein
1 Solma Smith
2 Elizabeth Tudor

Create DataFrame with index orientation

d = {0: ['Edward', 'Tudor'], 1: ['Robert', 'Redford'], 3: ['Earl', 'Scruggs']}
df = DataFrame.from_dict(d, orient='index')
df.columns=['first', 'last']
df
first last
0 Edward Tudor
1 Robert Redford
3 Earl Scruggs

Assign column names

d = {'a': 'A', 'b': 'B', 'c': 'C'}
df = DataFrame(list(d.items()), columns=['lower', 'upper'])
df
lower upper
0 a A
1 b B
2 c C

6.3 Convert characters to integers and back

Cast str to int

Base 10

int('011')

11

Base 2

int('011', 2)

3

Base 6

int('011', 6)

7

Base 8

int('011', 8)

9

Base 16

int('011', 16)

17

Cast int to string

one = str(1)
type(one)


str

6.4 Convert between hexadecimal, binary, and floats

Cast to str from float

a_str = str(12.4)
f" {a_str!r} is a {type(a_str)}"

" '12.4' is a <class 'str'>"

Cast to float from str

a_str = "12.3"
a_float = float(a_str)
f" {a_float!r} is a {type(a_float)}"

" 12.3 is a <class 'float'>"

Hexadecimal

Int to hex str

int_hex = hex(18)
f" hex(18) returns the {type(int_hex)}: {int_hex!r}"


" hex(18) returns the <class 'str'>: '0x12'"

Float to hex str

float_hex = 12.0.hex()
f" 12.4.hex() returns the {type(float_hex)}: {float_hex!r}"

" 12.4.hex() returns the <class 'str'>: '0x1.8000000000000p+3'"

hex function

Conversion to and from binary

Bytes literal

Similar to strings, but limited to ASCII characters.

bytes_str = b"some bytes literal"
type(bytes_str)

bytes

Encode to bytes

import base64
bytes_str = b"Encode this string"
encoded_str = base64.b64encode(bytes_str)
f"The encoded string {encoded_str!r} is of type {type(encoded_str)}"



"The encoded string b'RW5jb2RlIHRoaXMgc3RyaW5n' is of type <class 'bytes'>"

Decode from bytes

base64.b64decode(encoded_str)

b'Encode this string'

base64-module

Notes