0
# Path Templates
1

2
URI template expansion and validation for Google API resource paths, supporting variable substitution and path parameter extraction for RESTful API endpoints.
3

4
## Capabilities
5

6
### Template Expansion
7

8
```python { .api }
9
def expand(tmpl, *args, **kwargs):
10
    """
11
    Expand a path template with variables.
12
    
13
    Args:
14
        tmpl (str): Path template with {variable} placeholders
15
        *args: Positional arguments for template variables
16
        **kwargs: Named arguments for template variables
17
        
18
    Returns:
19
        str: Expanded path with variables substituted
20
    """
21

22
def validate(tmpl, path):
23
    """
24
    Validate that a path matches a template pattern.
25
    
26
    Args:
27
        tmpl (str): Path template pattern
28
        path (str): Path to validate
29
        
30
    Returns:
31
        dict: Extracted variables if path matches, raises ValueError if not
32
    """
33
```
34

35
### Field Manipulation
36

37
```python { .api }
38
def get_field(request, field):
39
    """
40
    Get field value from request dict or protobuf Message.
41
    
42
    Args:
43
        request: Request dict or protobuf Message
44
        field (str): Field path (e.g., "user.name" for nested fields)
45
        
46
    Returns:
47
        Any: Field value
48
    """
49

50
def delete_field(request, field):
51
    """
52
    Delete field from request dict or protobuf Message.
53
    
54
    Args:
55
        request: Request dict or protobuf Message  
56
        field (str): Field path to delete
57
    """
58

59
def transcode(http_options, message=None, **request_kwargs):
60
    """
61
    Transcode gRPC request to HTTP format.
62
    
63
    Args:
64
        http_options: HTTP binding configuration
65
        message: gRPC request message
66
        **request_kwargs: Additional request parameters
67
        
68
    Returns:
69
        dict: HTTP request components (method, uri, body)
70
    """
71
```
72

73
## Usage Examples
74

75
### Basic Path Template Usage
76

77
```python
78
from google.api_core import path_template
79

80
# Expand template with named parameters
81
template = "projects/{project}/instances/{instance}/databases/{database}"
82
path = path_template.expand(template, 
83
                           project="my-project",
84
                           instance="my-instance", 
85
                           database="my-db")
86
print(path)  # "projects/my-project/instances/my-instance/databases/my-db"
87

88
# Validate and extract parameters
89
extracted = path_template.validate(template, path)
90
print(extracted)  # {"project": "my-project", "instance": "my-instance", "database": "my-db"}
91
```