Python | Nested dictionary

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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 ‚Äã‚Äãcan 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: - {} 

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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 2022. 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:



Boris Sikorski

San Francisco | 2022-11-30

Simply put and clear. Thank you for sharing. Python | Nested dictionary and other issues with sep was always my weak point 😁. I am just not quite sure it is the best method

Anna Emmerson

Shanghai | 2022-11-30

Simply put and clear. Thank you for sharing. Python | Nested dictionary and other issues with repeat was always my weak point 😁. Checked yesterday, it works!

Davies Krasiko

London | 2022-11-30

Maybe there are another answers? What Python | Nested dictionary exactly means?. I am just not quite sure it is the best method

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