Glom module of Python data analysis module (1)

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Under the simple said glom The module is mainly used for processing structured data , Simple installation pip install  glom that will do , Next is glom Explain the method parameters with examples .

glom

With the same name as the module glom Method of use :

.glom(target, spec, **kwargs)
target Parameters are structured data , It's usually json Nested Type .
spec Parameters are defined templates
**kwargs Contains parameters of key value type :default,skip_exc,scope

Let's take a simple example 、

target = {'a': {'b':{'c':{'d':{'e':[1,2,3,4,5,6,7]}}}}}
spec = 'a.b.c.d.e'
output = glom(target, spec)
print(output)
# Output [1, 2, 3, 4, 5, 6, 7]
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Let's try more games :

target = {'a': {'b':{'c':{'d':{'e':[1,2,3,4,5,6,7]}}}}}
spec = {'aa':'a.b.c.d.e'}
output = glom(target, spec)
print(output)
# Output {'aa': [1, 2, 3, 4, 5, 6, 7]}

target2 = {'a': {'b':{'c':[{'d':[1,2,3,4]},{'d':[4,5,6,7]}]}}}
spec2 = {'test':('a.b.c',['d'])}
output2=glom(target2, spec2)
print(output2)
# Output {'test': [[1, 2, 3, 4], [4, 5, 6, 7]]}
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Another official example , Make comprehensive use of :

target = {'system': {'planets': [{'name': 'earth', 'moons': 1},
                                 {'name': 'jupiter', 'moons': 69}]}}

spec = {'names': ('system.planets', ['name']),
            'moons': ('system.planets', ['moons'])}
 Output :{'moons': [1, 69], 'names': ['earth', 'jupiter']}
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As can be seen from the above examples ,spec The basic usage is '' Write the key names in turn . Key name . Key name . Key name ,

Another thing to note , If there is a dictionary in the list to take its value, the key name must be the same, just above 'd' key .

.
It can be seen that glom and json It saves a lot of []. Easy to use , in addition spec The expression also supports the use of expressions, such as lambda.
Let's take a look at an example with complete parameters

target = {'a': [0, 1, 2]} # Given a structured data 
spec = {'a': ('a', [lambda x:x/x])}# obtain a The value of each element divided by its own value .
output = glom(target, spec,default='666',skip_exc=ZeroDivisionError)
print(output)
# Output 666
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The above results mainly demonstrate spec The advanced usage of and the usage of the third parameter . The above calculation 0/0 It's a mistake , Wrong type ZeroDivisionError, So we let ZeroDivisionError Error skipped , Simultaneous coordination default The default value when given an error .
But what if the following happens ？

t={'a': {'b.c':{'c':{'d':{'e':[1,2,3,4,5,6,7]}}}}}
s= {'aa':'a.b.c.c'}
print(glom(t,s))
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Now let's see Path Method

Path

glom.Path(*path_parts)
Path objects specify explicit paths when the default 'a.b.c'-style general access syntax won’t work or isn’t desirable. Use this to wrap ints, datetimes, and other valid keys, as well as strings with dots that shouldn’t be expanded, Let's look at an example .

from glom import glom,Path
target2 = {'a': {'b':{'c':[{'d':[1,2,3,4]},{'d':[4,5,6,7]}],'w':{'3.c':'e'}}}}
output2_1=Path(glom(target2,Path('a','b','w','3.c')))
print(output2_1)
# Output e
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Then let's go back and look at the use of spec Errors in the way

t={'a': {'b.c':{'c':{'d':{'e':[1,2,3,4,5,6,7]}}}}}
print(glom(t,{'aa':Path('a','b.c','c')}))
# Output {'aa': {'d': {'e': [1, 2, 3, 4, 5, 6, 7]}}}
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Be careful :

1.path The hierarchical relationship of the path must be next to . For example, I directly Path('a','c') It's going to be a mistake .
2.path You can't take the keys in the list like this. You need to cooperate glom Handle .
Path('system','planets','name') perhaps Path('system','planets',['name']) Neither. .

target = {'system': {'planets': [{'name': 'earth', 'moons': 1},
                                 {'name': 'jupiter', 'moons': 69}]}}

 follow-up ...
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