Python | Maketrans () and translate () Functions

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maketrans ()

The maketrans () function is used to build a transition table, i.e. specifies a list of characters to be replaced in the entire string, or characters to be removed from the string

Syntax: maketrans (str1, str2, str3)

Parameters:
str1: Specifies the list of characters that need to be replaced.
str2: Specifies the list of characters with which the characters need to be replaced.
str3: Specifies the list of characters that needs to be deleted.

Returns: Returns the translation table which specifies the conversions that can be used by translate ()

Translate with maketrans ()

For translating characters in a string, translate () is used to perform translations. This function uses the translation transform specified with maketrans ().

Syntax: translate (table, delstr)

Parameters:
table: Translate mapping specified to perform translations.
delstr: The delete string can be specified as optional argument is not mentioned in table.

Returns: Returns the argument string after performing the translations using the translation table.

Code no. 1: code for translation using translate () and maketrans ().

# Python3 demo code
# translations using
# maketrans () and translate ()


# uk Set for character translation

str1 = " wy "


# specify to replace with

str2 = "gf"


# remove characters

str3 = "u"


# target string

trg = "weeksyourweeks"


# using maketrans () for
# build translation
# table

tab le = trg.maketrans (str1, str2, str3)


# Print original line

print ( "The string before translating is:" , end = "")

print (trg)


# using translate () to translate.

print ( "The string after translating is: " , end = " ")

print (trg.translate (table))

Output:

 The string before translating is: weeksyourweeks The string after translating is: pythonengineering 

Translate without layouttrans ()

Translation can also be achieved by specifying the translation dictionary and passing as an object that acts as a display. In this case, there is no need for maketrans () to perform translations.

Code # 2: code for translation without layouttrans ().

# Python3 demo code
# no translations
# maketrans ( )


# display specification
# using ASCII

table = { 119 : 103 , 121 : 102 , 117 : None }


# target string

trg = "weeksyourweeks"


# Print original line

print ( "The string before translating is:" , end = " ")

print (trg)


# using translate () to translate.

print ( "The string after translating is:" , end = " ")

print (trg.translate (table))

Output:

 The string before translating is: weeksyourweeks The string after translating is: pythonengineering 

Application:
In many cases, errors can occur during coding or development, these functions provide simple and a quick way to replace and fix them and can potentially save you a lot of time.

Python | Maketrans () and translate () Functions __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 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:

Python | Maketrans () and translate () Functions __delete__: Questions

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]

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