| Section | Video Links |
|---|---|
| Visitor Overview |    |
| Visitor Use Case | |
| hasattr() Method | |
| expandtabs() Method | |
... Refer to Book or Design Patterns In Python website to read textual content.
... Refer to Book or Design Patterns In Python website to read textual content.
... Refer to Book or Design Patterns In Python website to read textual content.
python ./visitor/visitor_concept.py
D
B
C
A
561... Refer to Book or Design Patterns In Python website to read textual content.
python ./visitor/client.py
Utility :ABC-123-21
V8 engine :DEF-456-21
FrontLeft :GHI-789FL-21
FrontRight :GHI-789FR-21
BackLeft :GHI-789BL-21
BackRight :GHI-789BR-21
Total Price = 4132In the Visitor objects in the example use case above, I test if the elements have a certain attribute during the visit operation.
def visit(cls, element):
if hasattr(element, 'price'):
...The hasattr() method can be used to test if an instantiated object has an attribute of a particular name.
class ClassA():
name = "abc"
value = 123
CLASS_A = ClassA()
print(hasattr(CLASS_A, "name"))
print(hasattr(CLASS_A, "value"))
print(hasattr(CLASS_A, "date"))Outputs
True
True
FalseWhen printing strings to the console, you can include special characters \t that print a series of extra spaces called tabs. The tabs help present multiline text in a more tabular form which appears to be neater to look at.
abc 123
defg 456
hi 78910The number of spaces added depends on the size of the word before the \t character in the string. By default, a tab makes up 8 spaces.
Now, not all words separated by a tab will line up the same on the next line.
abcdef 123
cdefghij 4563
ghi 789
jklmn 1011
The problem occurs usually when a word is already 8 or more characters long.
To help solve the spacing issue, you can use the expandtabs() method on a string to set how many characters a tab will use.
print("abcdef\t123".expandtabs(10))
print("cdefghij\t4563".expandtabs(10))
print("ghi\t789".expandtabs(10))
print("jklmn\t1011".expandtabs(10))Now outputs
abcdef 123
cdefghij 4563
ghi 789
jklmn 1011... Refer to Book or Design Patterns In Python website to read textual content.