Python | Nested dictionary

| | | | | | | | | | | | | | | | |

👻 Check our latest review to choose the best laptop for Machine Learning engineers and Deep learning tasks!

A Dictionary in Python works similarly to a Dictionary in the real world. Dictionary keys must be unique and have an immutable data type such as strings, integers, and tuples, but the key values ​​can be repeated and of any type.

Nested Dictionary: Nested Dictionary means placing a dictionary in another dictionary. Nesting is very useful because the information that we can model in programs has expanded significantly.

nested_dict = { ’dict1’ : { ’ key_A’ : ’value_A’ },

’dict2’ : { ’key_B’ : ’ value_B’ }}

# As shown in the picture


# Create a nested dictionary

Dict = { 1 : ’Geeks’ , 2 : ’For’ , 3 : { ’ A’ : ’Welcome’ , ’ B’ : ’To’ , ’ C’ : ’Geeks’ }}

Creating a nested dictionary

In Python, a nested dictionary can be created by placing comma-separated dictionaries enclosed in curly braces.

# Blank nested dictionary

Dict = { ’Dict1’ : {},

’Dict2’ : {}}

print ( "Nested dictionary 1-" )

print ( Dict ) < / p>


# Sub-dictionary with the same keys

Dict = { ’Dict1’ : { ’name’ : ’ Ali’ , ’age’ : ’19’ },

’Dict2’ : { ’ name’ : ’Bob’ , ’ age’ : ’25’ }}

print ( "Nested dictionary 2- " )

print ( Dict )


# Sub-dictionary of mixed dictionary keys

Dict = { ’Dict1’ : { 1 : ’G’ , 2 : ’F’ , 3 : ’G’ },

’Dict2’ : { ’ Name’ : ’Geeks’ , 1 : [ 1 , 2 ]}}

print ( "Nested dictionary 3-" )

print ( Dict )

Exit :

 Nested dictionary 1- {’Dict1’: {},’ Dict2 ’: {}} Nested dictionary 2- {’ Dict1’: {’name’:’ Ali’, ’age’:’ 19’}, ’Dict2’: {’ name’: ’Bob’,’ age’: ’ 25’}} Nested dictionary 3- {’Dict1’: {1:’ G’, 2: ’F’, 3:’ G’}, ’Dict2’: {1: [1, 2],’ Name’: ’Geeks’}} 

Adding items to the nested dictionary

Adding items to nested a new dictionary can be done in several ways. One way to add a dictionary to a nested dictionary — is to add values ‚Äã‚Äãone by one, Nested_dict [dict] [key] = & # 39; value & # 39; . Another way — add the whole dictionary in one go, Nested_dict [dict] = {& # 39; key & # 39 ;: & # 39; value & # 39;} .

Dict = {}

print ( "Initial nested dictionary: -" )

print ( Dict )

Dict [ ’Dict1’ ] = {}


# Adding elements one at a time

Dict [ ’Dict1’ ] [ ’name’ ] = ’ Bob’

Dict [ ’Dict1’ ] [ ’age’ ] = 21

print ( "After adding dictionary Dict1" )

print ( Dict )


# Adding the entire dictionary

Dict [ ’Dict2’ ] = { ’ name’ : ’Cara’ , ’ age ’ : 25 }

print ( "After adding dictionary Dict1" )

print ( Dict )

Exit :

 Initial nested dictionary: - {} After adding dictionary Dict1 {’Dict1’: {’ age’: 21, ’name’:’ Bob’}} After adding dictionary Dict1 {’Dict1’: {’ age’: 21, ’name’:’ Bob’}, ’Dict2’: {’ age’: 25, ’name’:’ Cara’}} 

Accessing nested dictionary elements

To access the value of any key in a nested dictionary, use the syntax indexing [] .

# A nested dictionary with the same keys

Dict = { ’Dict1’ : { ’ name’ : ’Ali’ , ’ age ’ : ’ 19’ },

’Dict2’ : { ’name’ : ’ Bob’ , ’age’ : ’25’ }}


# Prints the value corresponding to the key & # 39; name & # 39; in Dict1

print ( Dict [ ’Dict1’ ] [ ’ name’ ])


# Prints the value corresponding to the age key in Dict2

print ( Dict [ ’Dict2’ ] [ ’age’ ])

Exit:

 Ali 25 

Deleting dictionaries from a nested dictionary

Deleting dictionaries from a nested dictionary can be done either using the del keyword or using the function pop () .

Dict = { ’Dict1’ : { ’ name ’ : ’ Ali’ , ’age’ : 19 },

’Dict2’ : { ’name’ : ’ Bob’ , ’age’ : 21 }}

print ( " Initial nest ed dictionary: - " )

print ( Dict )


# Delete the dictionary using the del keyword

print ( " Deleting Dict2: - " )

del Dict [ ’ Dict2’ ]

print ( Dict )


# Delete a dictionary using the pop function

print ( "Deleting Dict1: -" )

Dict . pop ( ’Dict1’ )

print ( Dict )

Exit:

 Initial nested dictionary: - {’Dict2’: {’ name ’:’ Bob’, ’age’: 21},’ Dict1’: {’name’:’ Ali’, ’age’: 19}} Deleting Dict2: - {’ Dict1’: {’name’:’ Ali’ , ’age’: 19}} Deleting Dict1: - {} 

👻 Read also: what is the best laptop for engineering students?

Python | Nested dictionary __del__: Questions

How can I make a time delay in Python?

5 answers

I would like to know how to put a time delay in a Python script.

2973

Answer #1

import time
time.sleep(5)   # Delays for 5 seconds. You can also use a float value.

Here is another example where something is run approximately once a minute:

import time
while True:
    print("This prints once a minute.")
    time.sleep(60) # Delay for 1 minute (60 seconds).

2973

Answer #2

You can use the sleep() function in the time module. It can take a float argument for sub-second resolution.

from time import sleep
sleep(0.1) # Time in seconds

Python | Nested dictionary __del__: Questions

How to delete a file or folder in Python?

5 answers

How do I delete a file or folder in Python?

2639

Answer #1


Path objects from the Python 3.4+ pathlib module also expose these instance methods:

2639

Answer #2


Path objects from the Python 3.4+ pathlib module also expose these instance methods:

2639

Answer #3

Python syntax to delete a file

import os
os.remove("/tmp/<file_name>.txt")

Or

import os
os.unlink("/tmp/<file_name>.txt")

Or

pathlib Library for Python version >= 3.4

file_to_rem = pathlib.Path("/tmp/<file_name>.txt")
file_to_rem.unlink()

Path.unlink(missing_ok=False)

Unlink method used to remove the file or the symbolik link.

If missing_ok is false (the default), FileNotFoundError is raised if the path does not exist.
If missing_ok is true, FileNotFoundError exceptions will be ignored (same behavior as the POSIX rm -f command).
Changed in version 3.8: The missing_ok parameter was added.

Best practice

  1. First, check whether the file or folder exists or not then only delete that file. This can be achieved in two ways :
    a. os.path.isfile("/path/to/file")
    b. Use exception handling.

EXAMPLE for os.path.isfile

#!/usr/bin/python
import os
myfile="/tmp/foo.txt"

## If file exists, delete it ##
if os.path.isfile(myfile):
    os.remove(myfile)
else:    ## Show an error ##
    print("Error: %s file not found" % myfile)

Exception Handling

#!/usr/bin/python
import os

## Get input ##
myfile= raw_input("Enter file name to delete: ")

## Try to delete the file ##
try:
    os.remove(myfile)
except OSError as e:  ## if failed, report it back to the user ##
    print ("Error: %s - %s." % (e.filename, e.strerror))

RESPECTIVE OUTPUT

Enter file name to delete : demo.txt
Error: demo.txt - No such file or directory.

Enter file name to delete : rrr.txt
Error: rrr.txt - Operation not permitted.

Enter file name to delete : foo.txt

Python syntax to delete a folder

shutil.rmtree()

Example for shutil.rmtree()

#!/usr/bin/python
import os
import sys
import shutil

# Get directory name
mydir= raw_input("Enter directory name: ")

## Try to remove tree; if failed show an error using try...except on screen
try:
    shutil.rmtree(mydir)
except OSError as e:
    print ("Error: %s - %s." % (e.filename, e.strerror))

Is there a simple way to delete a list element by value?

5 answers

I want to remove a value from a list if it exists in the list (which it may not).

a = [1, 2, 3, 4]
b = a.index(6)

del a[b]
print(a)

The above case (in which it does not exist) shows the following error:

Traceback (most recent call last):
  File "D:zjm_codea.py", line 6, in <module>
    b = a.index(6)
ValueError: list.index(x): x not in list

So I have to do this:

a = [1, 2, 3, 4]

try:
    b = a.index(6)
    del a[b]
except:
    pass

print(a)

But is there not a simpler way to do this?

1055

Answer #1

To remove an element"s first occurrence in a list, simply use list.remove:

>>> a = ["a", "b", "c", "d"]
>>> a.remove("b")
>>> print(a)
["a", "c", "d"]

Mind that it does not remove all occurrences of your element. Use a list comprehension for that.

>>> a = [10, 20, 30, 40, 20, 30, 40, 20, 70, 20]
>>> a = [x for x in a if x != 20]
>>> print(a)
[10, 30, 40, 30, 40, 70]

We hope this article has helped you to resolve the problem. Apart from Python | Nested dictionary, check other __del__-related topics.

Want to excel in Python? See our review of the best Python online courses 2023. If you are interested in Data Science, check also how to learn programming in R.

By the way, this material is also available in other languages:



Chen Danburry

Rome | 2023-03-23

Thanks for explaining! I was stuck with Python | Nested dictionary for some hours, finally got it done 🤗. Will get back tomorrow with feedback

Carlo Chamberlet

Vigrinia | 2023-03-23

Thanks for explaining! I was stuck with Python | Nested dictionary for some hours, finally got it done 🤗. Will get back tomorrow with feedback

Julia Sikorski

Prague | 2023-03-23

StackOverflow is always a bit confusing 😭 Python | Nested dictionary is not the only problem I encountered. I just hope that will not emerge anymore

Shop

Gifts for programmers

Learn programming in R: courses

$FREE
Gifts for programmers

Best Python online courses for 2022

$FREE
Gifts for programmers

Best laptop for Fortnite

$399+
Gifts for programmers

Best laptop for Excel

$
Gifts for programmers

Best laptop for Solidworks

$399+
Gifts for programmers

Best laptop for Roblox

$399+
Gifts for programmers

Best computer for crypto mining

$499+
Gifts for programmers

Best laptop for Sims 4

$

Latest questions

PythonStackOverflow

Common xlabel/ylabel for matplotlib subplots

1947 answers

PythonStackOverflow

Check if one list is a subset of another in Python

1173 answers

PythonStackOverflow

How to specify multiple return types using type-hints

1002 answers

PythonStackOverflow

Printing words vertically in Python

909 answers

PythonStackOverflow

Python Extract words from a given string

798 answers

PythonStackOverflow

Why do I get "Pickle - EOFError: Ran out of input" reading an empty file?

606 answers

PythonStackOverflow

Python os.path.join () method

384 answers

PythonStackOverflow

Flake8: Ignore specific warning for entire file

360 answers

News


Wiki

Python | How to copy data from one Excel sheet to another

Common xlabel/ylabel for matplotlib subplots

Check if one list is a subset of another in Python

How to specify multiple return types using type-hints

Printing words vertically in Python

Python Extract words from a given string

Cyclic redundancy check in Python

Finding mean, median, mode in Python without libraries

Python add suffix / add prefix to strings in a list

Why do I get "Pickle - EOFError: Ran out of input" reading an empty file?

Python - Move item to the end of the list

Python - Print list vertically