Example code for analyzing Python Boolean values

Boolean represents one of two values: True or False.

Boolean values

In programming, you often need to know whether an expression is True or False.

You can evaluate any expression in Python and get one of two answers, True or False.

When comparing two values, the expression is evaluated and Python returns a Boolean answer:

Example

print(8 > 7)
print(8 == 7)
print(8 < 7)

Running Example

When a condition is run in an if statement, Python returns True or False:

Example

According to whether the condition is true Still wrong, prints a message:

a = 200
b = 33

if b > a:
  print("b is greater than a")
else:
  print("b is not greater than a")

Run the instance

Evaluate values ​​and variables

The bool() function allows you to evaluate any value and returns True or False for you.

Example

Evaluate strings and numbers:

print(bool("Hello"))
print(bool(10))

Run Example

##Example

Evaluate two variables:

x = "Hello"
y = 10

print(bool(x))
print(bool(y))

Running Example

Most values ​​are True

If there is something, almost all values ​​will evaluate to True.

Any string except the empty string is True.

Any number except 0 is True.

True for any list, tuple, set, and dictionary except empty lists.

Instance

The following example will return True:

bool("abc")
bool(123)
bool(["apple", "cherry", "banana"])

Run instance

someone These values ​​are False

In fact, not many values ​​will evaluate to False except null values ​​(such as (), [], {}, "", the number 0, and the value None). Of course, the value False evaluates to False.

Example

The following example will return False:

bool(False)
bool(None)
bool(0)
bool("")
bool(())
bool([])
bool({})

Run the example

Here A value or object evaluates to False if the object is generated by a class with a

len function that returns 0 or False:

Example

class myclass():
  def __len__(self):
    return 0

myobj = myclass()
print(bool(myobj))

Run the example

Function can return Boolean

Python also has many built-in functions that return Boolean values, such as isinstance() function, which can be used to determine whether an object has a certain data type:

Instance

Check whether the object is an integer:

x = 200
print(isinstance(x, int))

Running instance

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