Python key exist or not?

Question

How to know key exists in Python?

Import the os module:

import os

To get an environment variable:

os.environ.get('Env_var')

To set an environment variable:

# Set environment variables
os.environ['Env_var'] = 'Some Value'

Asked By: ankor ank

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Source

Answer 1

Using if statement: You can simply check using an if statement:

if os.getenv('Env_var') is not None:
    val = os.getenv('Env_var')
    print(f'Value is {val}')
else:
    print('Entry not found!')

Using default value: Alternatively, you can use the dictionary’s get function to retrieve the value associated with the key or return a default value if the entry does not exist. This may be useful if you wish to assign a default value for processing.

val = os.getenv('Env_var', -1)

if val == -1:
    print('Entry not found!')
else:
    print(f'Value is {val}')

Answered By: Prins

Answer 2

Check If Key Exists using the Inbuilt method keys()

def checkKey(dic, key):
    if key in dic.keys():
        print("Present, ", end =" ")
        print("value =", dic[key])
    else:
        print("Not present")
         
# Driver Code
dic = {'a': 100, 'b':200, 'c':300}
key = 'b'
checkKey(dic, key)
 
key = 'w'
checkKey(dic, key)

Output:
Present, value = 200
Not present

Check If Key Exists using if and in

def checkKey(dic, key):
     
    if key in dic:
        print("Present, ", end =" ")
        print("value =", dic[key])
    else:
        print("Not present")
 
# Driver Code
dic = {'a': 100, 'b':200, 'c':300}
key = 'b'
checkKey(dic, key)
 
key = 'w'
checkKey(dic, key)

Output:
Present, value = 200
Not present

Check If Key Exists using has_key() method

def checkKey(dic, key):
     
    if dic.has_key(key):
        print("Present, value =", dic[key])
    else:
        print("Not present")
 
# Driver Function
dic = {'a': 100, 'b':200, 'c':300}
key = 'b'
checkKey(dic, key)
 
key = 'w'
checkKey(dic, key)

Output:
Present, value = 200
Not present

Check If Key Exists using get()

dic = {'a': 100, 'b':200, 'c':300}
 
# cheack if "b" is none or not.
if dic.get('b') == None:
  print("Not Present")
else:
  print("Present")

Output:
Present

Answered By: unknown code

Python key exist or not?

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