How to reindex an array in PHP?

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Re-indexing an array can be done with some built-in function together. These functions are:
  • array_combine() function :Function array_combine() - it is a built-in function in PHP that is used to combine two arrays and create a new array using one array for keys and another array for values. That is, all the elements of one array will be the keys of the new array, and all the elements of the second array will be the values ‚Äã‚Äãof this new array.
  • Function range(): function range() - it is a built-in function in PHP that is used to create an array of elements of any type, such as integers, alphabets in a given range (from low to high), i.e. the first element of the list is considered low and the last one is considered high.
  • count() Function : function count() is used to count the current elements in an array. The function can return 0 for a variable that has been set to an empty array. Also, for a variable that is not set, the function returns 0.
  • array_values ‚Äã‚Äã() Function :This function is used to get an array of values ‚Äã‚Äãfrom another array, which can contain key-value pairs or just values. The function creates another array that stores all the values ‚Äã‚Äãand by default assigns numeric keys to the values.
We will use array_values ‚Äã‚Äã() to get all the values ‚Äã‚Äãof array and range() to create an array elements that we want to use as new keys or new array index (reindexing). Then the array_combine() function will combine the array as keys and values.Example 1:
// Declare an associative array $arr = array ( 0 = > ’Tony’ , 1 = > ’Stark’ , 2 = > ’Iron’ , 3 = > ’Man’
); echo " Array before re-indexing " ;
// Using a foreach loop to print array elements foreach ( $arr as $key = > $value ) { echo "Index:" . $key . "Value:" . $value . "" ; }
// Set a sequential number of three $New_start_index = 3; $arr = array_combine (range ( $New_start_index , count ( $arr ) + ( $New_start_index - 1)), array_values ‚Äã‚Äã ( $arr )); echo " Array after re-indexing " ;
// Using a foreach loop to print array elements foreach ( $arr as $key = > $value ) { echo "Index:" . $key . "Value:" . $value . "" ; }
?>
Exit:
Array before re -indexing Index: 0 Value: Tony Index: 1 Value: Stark Index: 2 Value: Iron Index: 3 Value: Man Array after re-indexing Index: 3 Value: Tony Index: 4 Value: Stark Index: 5 Value: Iron Index : 6 Value: Man 
Example 2.Add some data to the beginning of the array and then extract the array from the index.
// Declare an associative array $arr = array ( 0 = > ’Tony’ , 1 = > ’Stark’ , 2 = > ’Iron’ , 3 = > ’Man’); echo " Array before re-indexing " ;
// Using a foreach loop to print array elements foreach ( $arr as $key = > $value ) { echo "Index:" . $key . "Value:" . $value . "" ; }
// Set a sequential number of three $New_start_index = 3; $raw_data = range (0, $New_start_index - 1);
// Add data to the beginning of the array foreach ( $raw_data as $key = > $value ) { array_unshift ( $arr , $value ); } $arr = array_values ‚Äã‚Äã ( $arr );
// Remove unnecessary index so we start at 10 $arr = array_slice ( $arr , $New_start_index , count ( $arr ), true); echo "Array after re indexing" ;
// Using a foreach loop to print an array foreach ( $arr as $key = > $value ) { echo "Index:" . $key . "Value:" . $value . "" ; }
?>
Exit:
Array before re -indexing Index: 0 Value: Tony Index: 1 Value: Stark Index: 2 Value: Iron Index: 3 Value: Man Array after re indexing Index: 3 Value: Tony Index: 4 Value: Stark Index: 5 Value: Iron Index: 6 Value: Man 
In this example, first add some data to the array, and for that we do it again with a loop, and then delete the data we added, so this is also not the best choice for re-indexing the array ... This method is not suitable for reindexing alphabetic keys.Example 3:This example reindexes an alphabetical array ’ p & # 39 ;. Two additional functions are used to reindex alphabets:
  • Function ord() :The ord() function - is a built-in PHP function that returns the ASCII value of the first character of a string.
  • CHR() Function:The CHR() function is a built-in function in PHP that is used to convert an ASCII value to a character.

// Declare an associative array $arr = array ( ’a’ = > ’India’ , ’b’ = > ’America’ , ’c’ = > ’Russia’ , ’d’ = > ’China’); echo " Array before re-indexing " ;
// Using a foreach loop to print array elements foreach ( $arr as $key = > $value ) { echo "Index:" . $key . "Value:" . $value . "" ; }
// Set index from ’ p ’ $New_start_index = ’ p’ ;
// The ord() function is used to get the ascii value
// chr() function to convert a number to ASCII $arr = array_combine (range ( $New_start_index , chr ( count ( $arr ) + (ord ( $New_start_index ) - 1))), array_values ‚Äã‚Äã ( $arr )); echo " Array after re indexing " ;
// Using a foreach loop to print an array foreach ( $arr as $key = > $value ) { echo "Index:" . $key . "Value:" . $value . "" ; }
?>
Exit:
Array before re -indexing Index: a Value: India Index: b Value: America Index: c Value: Russia Index: d Value: China Array after re indexing Index: p Value: India Index: q Value: America Index: r Value: Russia Index: s Value: China 

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How to reindex an array in PHP? __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

How to reindex an array in PHP? __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 How to reindex an array in PHP?, 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:



Frank Wu

San Francisco | 2023-03-21

UI PHP module is always a bit confusing 😭 How to reindex an array in PHP? is not the only problem I encountered. Will get back tomorrow with feedback

Olivia Emmerson

San Francisco | 2023-03-21

Simply put and clear. Thank you for sharing. How to reindex an array in PHP? and other issues with code Python module was always my weak point 😁. Will use it in my bachelor thesis

Manuel Porretti

Singapore | 2023-03-21

Maybe there are another answers? What How to reindex an array in PHP? exactly means?. Checked yesterday, it works!

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