Python Conditions

 

Conditions

Python uses boolean logic to evaluate conditions. The boolean values True and False are returned when an expression is compared or evaluated. For example:

Program:

x = 2 print(x == 2)  print(x == 3)  print(x < 3) # Scripts Ends

Output:

True False True

Notice that variable assignment is done using a single equals operator "=", whereas comparison between two variables is done using the double equals operator "==". The "not equals" operator is marked as "!=".

 

1. Boolean operators

The "and", "or"  and "not" boolean operators allow building complex boolean expressions, for example:

Program:

name = "Balaji" age = 50 if name == "Balaji" and age == 50:     print("Your name is Blaji, and you are also 50 years old.") if name == "Cris" or name == "Roky":     print("Your name is either Cris or Roky.") print(not(age <= 32))   print(not(age <= 62))   # Scripts Ends

Output:

Your name is Blaji, and you are also 50 years old. True False

2. The "in" operator

The "in" operator could be used to check if a specified object exists within an iterable object container, such as a list:

Program:

name = "BalajiTech" if name in ["Balaji", "BalajiTech"]:     print("Your name is either BalajiTech or Balaji.") # Scripts Ends

Output:

Your name is either BalajiTech or Balaji.

Python uses indentation to define code blocks, instead of brackets. The standard Python indentation is 4 spaces, although tabs and any other space size will work, as long as it is consistent. Notice that code blocks do not need any termination.

Here is an example for using Python's "if" statement using code blocks:

Program:

statement = False another_statement = True if statement is True:     # do something     pass elif another_statement is True: # else if     # do something else     pass else:     # do another thing     pass # Scripts Ends

Output:

A statement is evaulated as true if one of the following is correct: 1. The "True" boolean variable is given, or calculated using an expression, such as an arithmetic comparison. 2. An object which is not considered "empty" is passed.

Here are some examples for objects which are considered as empty: 1. An empty string: "" 2. An empty list: [] 3. The number zero: 0 4. The false boolean variable: False

3. The 'is' and 'not' operator

Unlike the double equals operator "==", the "is" operator does not match the values of the variables, but the instances themselves. Using "not" before a boolean expression inverts it For example:

Program:

x = [1,2,3] y = [1,2,3] print(x == y) # Prints out True print(x is y) # Prints out False print(not False) # Prints out True print((not False) == (False)) # Prints out False # Scripts Ends

Output:

True False True False