Movatterモバイル変換

Python Library Reference

Previous:2.2 Built-in TypesUp:2.2 Built-in TypesNext:2.2.2 Boolean Operations

---

 
2.2.1 Truth Value Testing

Any object can be tested for truth value, for use in anif orwhile condition or as operand of the Boolean operations below.The following values are considered false: 

• None 

• False 

• zero of any numeric type, for example,0,0L,0.0,0j.

• any empty sequence, for example,'',(),[].

• any empty mapping, for example,{}.

• instances of user-defined classes, if the class defines a__nonzero__() or__len__() method, when that method returns the integer zero orbool valueFalse.^2.5

All other values are considered true -- so objects of many types arealways true. 

Operations and built-in functions that have a Boolean result alwaysreturn0 for false and1 for true, unless otherwisestated. (Important exception: the Boolean operations"or" and "and" always return one oftheir operands.)

Footnotes

...False.^2.5

Additional information on these special methods may be found in thePython Reference Manual.

---

Python Library Reference

Previous:2.2 Built-in TypesUp:2.2 Built-in TypesNext:2.2.2 Boolean Operations

---

Release 2.2.3, documentation updated on 30 May 2003.