I'm using Jinja on my site and I like it.
I've come across a simple need. How to display today's date? Is there a way to inline some Python code in a Jinja template?
import datetime
now = datetime.datetime.utcnow()
print now.strftime("%Y-%m-%d %H:%M")
This article says no, but suggests using a macro or a filter?
Really? Must we resort to all that? OK, what would that look like in this case?
No, there is no way to inline Python into Jinja. However, you can add to the constructs that Jinja knows by extending the Environment of the template engine or the global namespace available to all templates. Alternately, you can add a filter that let's you format datetime objects.
Flask stores the Jinja2 Environment on app.jinja_env. You can inject new context into the environment by either adding to this dictionary directly, or by using the #app.context_processor decorator.
Whatever path you choose, this should be done while you are setting up the application, before you have served any requests. (See the snippets section of the website for some good examples of how to set up filters - the docs contain a good example of adding to the global variables).
The current answers are correct for pretty much every situation. However there are some very rare cases where you would want to have python code inside the template. In my case I want to use it to preprocess some latex files and I would prefer to keep the python code generating table values, plots, etc, inside the latex file it self.
So I made a Jinja2 extension that adds a new "py" block allowing python code to be written inside the template. Please keep in mind that I had to do some questionable work-arounds to get this to work, so I'm not 100% sure in which situations it fails or behaves unexpectedly.
This is an example template.
Foo was given to the template
foo: {{ foo }}
Bar was not, so it is missing
bar is missing: {{ bar == missing }}
{% py %}
# Normal python code in here
# Excess indentation will be removed.
# All template variables are accessible and can be modified.
import numpy as np
a = np.array([1, 2])
m = np.array([[3, 4], [5, 6]])
bar = m # a * foo
# It's also possible to template the python code.
{% if change_foo %}
foo = 'new foo value'
{% endif %}
print("Stdio is redirected to the output.")
{% endpy %}
Foo will have the new value if you set change_foo to True
foo: {{ foo }}
Bar will now have a value.
bar: {{ bar }}
{% py %}
# The locals from previous blocks are accessible.
m = m**2
{% endpy %}
m:
{{ m }}
The output if we set the template parameters to foo=10, change_foo=True is:
Foo was given to the template
foo: 10
Bar was not, so it is missing
bar is missing: True
Stdio is redirected to the output.
Foo will have the new value if you set change_foo to True
foo: new foo value
Bar will now have a value.
bar: [110 170]
m:
[[ 9 16]
[25 36]]
The extension with a main function to run the example.
from jinja2 import Environment, PackageLoader, nodes
from jinja2.ext import Extension
from textwrap import dedent
from io import StringIO
import sys
import re
import ctypes
def main():
env = Environment(
loader=PackageLoader('python_spike', 'templates'),
extensions=[PythonExtension]
)
template = env.get_template('emb_py2.txt')
print(template.render(foo=10, change_foo=True))
var_name_regex = re.compile(r"l_(\d+)_(.+)")
class PythonExtension(Extension):
# a set of names that trigger the extension.
tags = {'py'}
def __init__(self, environment: Environment):
super().__init__(environment)
def parse(self, parser):
lineno = next(parser.stream).lineno
body = parser.parse_statements(['name:endpy'], drop_needle=True)
return nodes.CallBlock(self.call_method('_exec_python',
[nodes.ContextReference(), nodes.Const(lineno), nodes.Const(parser.filename)]),
[], [], body).set_lineno(lineno)
def _exec_python(self, ctx, lineno, filename, caller):
# Remove access indentation
code = dedent(caller())
# Compile the code.
compiled_code = compile("\n"*(lineno-1) + code, filename, "exec")
# Create string io to capture stdio and replace it.
sout = StringIO()
stdout = sys.stdout
sys.stdout = sout
try:
# Execute the code with the context parents as global and context vars and locals.
exec(compiled_code, ctx.parent, ctx.vars)
except Exception:
raise
finally:
# Restore stdout whether the code crashed or not.
sys.stdout = stdout
# Get a set of all names in the code.
code_names = set(compiled_code.co_names)
# The the frame in the jinja generated python code.
caller_frame = sys._getframe(2)
# Loop through all the locals.
for local_var_name in caller_frame.f_locals:
# Look for variables matching the template variable regex.
match = re.match(var_name_regex, local_var_name)
if match:
# Get the variable name.
var_name = match.group(2)
# If the variable's name appears in the code and is in the locals.
if (var_name in code_names) and (var_name in ctx.vars):
# Copy the value to the frame's locals.
caller_frame.f_locals[local_var_name] = ctx.vars[var_name]
# Do some ctypes vodo to make sure the frame locals are actually updated.
ctx.exported_vars.add(var_name)
ctypes.pythonapi.PyFrame_LocalsToFast(
ctypes.py_object(caller_frame),
ctypes.c_int(1))
# Return the captured text.
return sout.getvalue()
if __name__ == "__main__":
main()
You can add to global variables which can be accessed from Jinja templates. You can put your own function definitions in there, which do whatever you need.
Given the following format (.properties or .ini):
propertyName1=propertyValue1
propertyName2=propertyValue2
...
propertyNameN=propertyValueN
For Java there is the Properties class that offers functionality to parse / interact with the above format.
Is there something similar in python's standard library (2.x) ?
If not, what other alternatives do I have ?
I was able to get this to work with ConfigParser, no one showed any examples on how to do this, so here is a simple python reader of a property file and example of the property file. Note that the extension is still .properties, but I had to add a section header similar to what you see in .ini files... a bit of a bastardization, but it works.
The python file: PythonPropertyReader.py
#!/usr/bin/python
import ConfigParser
config = ConfigParser.RawConfigParser()
config.read('ConfigFile.properties')
print config.get('DatabaseSection', 'database.dbname');
The property file: ConfigFile.properties
[DatabaseSection]
database.dbname=unitTest
database.user=root
database.password=
For more functionality, read: https://docs.python.org/2/library/configparser.html
For .ini files there is the configparser module that provides a format compatible with .ini files.
Anyway there's nothing available for parsing complete .properties files, when I have to do that I simply use jython (I'm talking about scripting).
I know that this is a very old question, but I need it just now and I decided to implement my own solution, a pure python solution, that covers most uses cases (not all):
def load_properties(filepath, sep='=', comment_char='#'):
"""
Read the file passed as parameter as a properties file.
"""
props = {}
with open(filepath, "rt") as f:
for line in f:
l = line.strip()
if l and not l.startswith(comment_char):
key_value = l.split(sep)
key = key_value[0].strip()
value = sep.join(key_value[1:]).strip().strip('"')
props[key] = value
return props
You can change the sep to ':' to parse files with format:
key : value
The code parses correctly lines like:
url = "http://my-host.com"
name = Paul = Pablo
# This comment line will be ignored
You'll get a dict with:
{"url": "http://my-host.com", "name": "Paul = Pablo" }
A java properties file is often valid python code as well. You could rename your myconfig.properties file to myconfig.py. Then just import your file, like this
import myconfig
and access the properties directly
print myconfig.propertyName1
if you don't have multi line properties and a very simple need, a few lines of code can solve it for you:
File t.properties:
a=b
c=d
e=f
Python code:
with open("t.properties") as f:
l = [line.split("=") for line in f.readlines()]
d = {key.strip(): value.strip() for key, value in l}
If you have an option of file formats I suggest using .ini and Python's ConfigParser as mentioned. If you need compatibility with Java .properties files I have written a library for it called jprops. We were using pyjavaproperties, but after encountering various limitations I ended up implementing my own. It has full support for the .properties format, including unicode support and better support for escape sequences. Jprops can also parse any file-like object while pyjavaproperties only works with real files on disk.
This is not exactly properties but Python does have a nice library for parsing configuration files. Also see this recipe: A python replacement for java.util.Properties.
i have used this, this library is very useful
from pyjavaproperties import Properties
p = Properties()
p.load(open('test.properties'))
p.list()
print(p)
print(p.items())
print(p['name3'])
p['name3'] = 'changed = value'
Here is link to my project: https://sourceforge.net/projects/pyproperties/. It is a library with methods for working with *.properties files for Python 3.x.
But it is not based on java.util.Properties
This is a one-to-one replacement of java.util.Propeties
From the doc:
def __parse(self, lines):
""" Parse a list of lines and create
an internal property dictionary """
# Every line in the file must consist of either a comment
# or a key-value pair. A key-value pair is a line consisting
# of a key which is a combination of non-white space characters
# The separator character between key-value pairs is a '=',
# ':' or a whitespace character not including the newline.
# If the '=' or ':' characters are found, in the line, even
# keys containing whitespace chars are allowed.
# A line with only a key according to the rules above is also
# fine. In such case, the value is considered as the empty string.
# In order to include characters '=' or ':' in a key or value,
# they have to be properly escaped using the backslash character.
# Some examples of valid key-value pairs:
#
# key value
# key=value
# key:value
# key value1,value2,value3
# key value1,value2,value3 \
# value4, value5
# key
# This key= this value
# key = value1 value2 value3
# Any line that starts with a '#' is considerered a comment
# and skipped. Also any trailing or preceding whitespaces
# are removed from the key/value.
# This is a line parser. It parses the
# contents like by line.
You can use a file-like object in ConfigParser.RawConfigParser.readfp defined here -> https://docs.python.org/2/library/configparser.html#ConfigParser.RawConfigParser.readfp
Define a class that overrides readline that adds a section name before the actual contents of your properties file.
I've packaged it into the class that returns a dict of all the properties defined.
import ConfigParser
class PropertiesReader(object):
def __init__(self, properties_file_name):
self.name = properties_file_name
self.main_section = 'main'
# Add dummy section on top
self.lines = [ '[%s]\n' % self.main_section ]
with open(properties_file_name) as f:
self.lines.extend(f.readlines())
# This makes sure that iterator in readfp stops
self.lines.append('')
def readline(self):
return self.lines.pop(0)
def read_properties(self):
config = ConfigParser.RawConfigParser()
# Without next line the property names will be lowercased
config.optionxform = str
config.readfp(self)
return dict(config.items(self.main_section))
if __name__ == '__main__':
print PropertiesReader('/path/to/file.properties').read_properties()
If you need to read all values from a section in properties file in a simple manner:
Your config.properties file layout :
[SECTION_NAME]
key1 = value1
key2 = value2
You code:
import configparser
config = configparser.RawConfigParser()
config.read('path_to_config.properties file')
details_dict = dict(config.items('SECTION_NAME'))
This will give you a dictionary where keys are same as in config file and their corresponding values.
details_dict is :
{'key1':'value1', 'key2':'value2'}
Now to get key1's value :
details_dict['key1']
Putting it all in a method which reads that section from config file only once(the first time the method is called during a program run).
def get_config_dict():
if not hasattr(get_config_dict, 'config_dict'):
get_config_dict.config_dict = dict(config.items('SECTION_NAME'))
return get_config_dict.config_dict
Now call the above function and get the required key's value :
config_details = get_config_dict()
key_1_value = config_details['key1']
-------------------------------------------------------------
Extending the approach mentioned above, reading section by section automatically and then accessing by section name followed by key name.
def get_config_section():
if not hasattr(get_config_section, 'section_dict'):
get_config_section.section_dict = dict()
for section in config.sections():
get_config_section.section_dict[section] =
dict(config.items(section))
return get_config_section.section_dict
To access:
config_dict = get_config_section()
port = config_dict['DB']['port']
(here 'DB' is a section name in config file
and 'port' is a key under section 'DB'.)
create a dictionary in your python module and store everything into it and access it, for example:
dict = {
'portalPath' : 'www.xyx.com',
'elementID': 'submit'}
Now to access it you can simply do:
submitButton = driver.find_element_by_id(dict['elementID'])
My Java ini files didn't have section headers and I wanted a dict as a result. So i simply injected an "[ini]" section and let the default config library do its job.
Take a version.ini fie of the eclipse IDE .metadata directory as an example:
#Mon Dec 20 07:35:29 CET 2021
org.eclipse.core.runtime=2
org.eclipse.platform=4.19.0.v20210303-1800
# 'injected' ini section
[ini]
#Mon Dec 20 07:35:29 CET 2021
org.eclipse.core.runtime=2
org.eclipse.platform=4.19.0.v20210303-1800
The result is converted to a dict:
from configparser import ConfigParser
#staticmethod
def readPropertyFile(path):
# https://stackoverflow.com/questions/3595363/properties-file-in-python-similar-to-java-properties
config = ConfigParser()
s_config= open(path, 'r').read()
s_config="[ini]\n%s" % s_config
# https://stackoverflow.com/a/36841741/1497139
config.read_string(s_config)
items=config.items('ini')
itemDict={}
for key,value in items:
itemDict[key]=value
return itemDict
This is what I'm doing in my project: I just create another .py file called properties.py which includes all common variables/properties I used in the project, and in any file need to refer to these variables, put
from properties import *(or anything you need)
Used this method to keep svn peace when I was changing dev locations frequently and some common variables were quite relative to local environment. Works fine for me but not sure this method would be suggested for formal dev environment etc.
import json
f=open('test.json')
x=json.load(f)
f.close()
print(x)
Contents of test.json:
{"host": "127.0.0.1", "user": "jms"}
I have created a python module that is almost similar to the Properties class of Java ( Actually it is like the PropertyPlaceholderConfigurer in spring which lets you use ${variable-reference} to refer to already defined property )
EDIT : You may install this package by running the command(currently tested for python 3).
pip install property
The project is hosted on GitHub
Example : ( Detailed documentation can be found here )
Let's say you have the following properties defined in my_file.properties file
foo = I am awesome
bar = ${chocolate}-bar
chocolate = fudge
Code to load the above properties
from properties.p import Property
prop = Property()
# Simply load it into a dictionary
dic_prop = prop.load_property_files('my_file.properties')
Below 2 lines of code shows how to use Python List Comprehension to load 'java style' property file.
split_properties=[line.split("=") for line in open('/<path_to_property_file>)]
properties={key: value for key,value in split_properties }
Please have a look at below post for details
https://ilearnonlinesite.wordpress.com/2017/07/24/reading-property-file-in-python-using-comprehension-and-generators/
you can use parameter "fromfile_prefix_chars" with argparse to read from config file as below---
temp.py
parser = argparse.ArgumentParser(fromfile_prefix_chars='#')
parser.add_argument('--a')
parser.add_argument('--b')
args = parser.parse_args()
print(args.a)
print(args.b)
config file
--a
hello
--b
hello dear
Run command
python temp.py "#config"
You could use - https://pypi.org/project/property/
eg - my_file.properties
foo = I am awesome
bar = ${chocolate}-bar
chocolate = fudge
long = a very long property that is described in the property file which takes up \
multiple lines can be defined by the escape character as it is done here
url=example.com/api?auth_token=xyz
user_dir=${HOME}/test
unresolved = ${HOME}/files/${id}/${bar}/
fname_template = /opt/myapp/{arch}/ext/{objid}.dat
Code
from properties.p import Property
## set use_env to evaluate properties from shell / os environment
prop = Property(use_env = True)
dic_prop = prop.load_property_files('my_file.properties')
## Read multiple files
## dic_prop = prop.load_property_files('file1', 'file2')
print(dic_prop)
# Output
# {'foo': 'I am awesome', 'bar': 'fudge-bar', 'chocolate': 'fudge',
# 'long': 'a very long property that is described in the property file which takes up multiple lines
# can be defined by the escape character as it is done here', 'url': 'example.com/api?auth_token=xyz',
# 'user_dir': '/home/user/test',
# 'unresolved': '/home/user/files/${id}/fudge-bar/',
# 'fname_template': '/opt/myapp/{arch}/ext/{objid}.dat'}
I did this using ConfigParser as follows. The code assumes that there is a file called config.prop in the same directory where BaseTest is placed:
config.prop
[CredentialSection]
app.name=MyAppName
BaseTest.py:
import unittest
import ConfigParser
class BaseTest(unittest.TestCase):
def setUp(self):
__SECTION = 'CredentialSection'
config = ConfigParser.ConfigParser()
config.readfp(open('config.prop'))
self.__app_name = config.get(__SECTION, 'app.name')
def test1(self):
print self.__app_name % This should print: MyAppName
This is what i had written to parse file and set it as env variables which skips comments and non key value lines added switches to specify
hg:d
-h or --help print usage summary
-c Specify char that identifies comment
-s Separator between key and value in prop file
and specify properties file that needs to be parsed eg : python
EnvParamSet.py -c # -s = env.properties
import pipes
import sys , getopt
import os.path
class Parsing :
def __init__(self , seprator , commentChar , propFile):
self.seprator = seprator
self.commentChar = commentChar
self.propFile = propFile
def parseProp(self):
prop = open(self.propFile,'rU')
for line in prop :
if line.startswith(self.commentChar)==False and line.find(self.seprator) != -1 :
keyValue = line.split(self.seprator)
key = keyValue[0].strip()
value = keyValue[1].strip()
print("export %s=%s" % (str (key),pipes.quote(str(value))))
class EnvParamSet:
def main (argv):
seprator = '='
comment = '#'
if len(argv) is 0:
print "Please Specify properties file to be parsed "
sys.exit()
propFile=argv[-1]
try :
opts, args = getopt.getopt(argv, "hs:c:f:", ["help", "seprator=","comment=", "file="])
except getopt.GetoptError,e:
print str(e)
print " possible arguments -s <key value sperator > -c < comment char > <file> \n Try -h or --help "
sys.exit(2)
if os.path.isfile(args[0])==False:
print "File doesnt exist "
sys.exit()
for opt , arg in opts :
if opt in ("-h" , "--help"):
print " hg:d \n -h or --help print usage summary \n -c Specify char that idetifes comment \n -s Sperator between key and value in prop file \n specify file "
sys.exit()
elif opt in ("-s" , "--seprator"):
seprator = arg
elif opt in ("-c" , "--comment"):
comment = arg
p = Parsing( seprator, comment , propFile)
p.parseProp()
if __name__ == "__main__":
main(sys.argv[1:])
Lightbend has released the Typesafe Config library, which parses properties files and also some JSON-based extensions. Lightbend's library is only for the JVM, but it seems to be widely adopted and there are now ports in many languages, including Python: https://github.com/chimpler/pyhocon
You can use the following function, which is the modified code of #mvallebr. It respects the properties file comments, ignores empty new lines, and allows retrieving a single key value.
def getProperties(propertiesFile ="/home/memin/.config/customMemin/conf.properties", key=''):
"""
Reads a .properties file and returns the key value pairs as dictionary.
if key value is specified, then it will return its value alone.
"""
with open(propertiesFile) as f:
l = [line.strip().split("=") for line in f.readlines() if not line.startswith('#') and line.strip()]
d = {key.strip(): value.strip() for key, value in l}
if key:
return d[key]
else:
return d
this works for me.
from pyjavaproperties import Properties
p = Properties()
p.load(open('test.properties'))
p.list()
print p
print p.items()
print p['name3']
I followed configparser approach and it worked quite well for me. Created one PropertyReader file and used config parser there to ready property to corresponding to each section.
**Used Python 2.7
Content of PropertyReader.py file:
#!/usr/bin/python
import ConfigParser
class PropertyReader:
def readProperty(self, strSection, strKey):
config = ConfigParser.RawConfigParser()
config.read('ConfigFile.properties')
strValue = config.get(strSection,strKey);
print "Value captured for "+strKey+" :"+strValue
return strValue
Content of read schema file:
from PropertyReader import *
class ReadSchema:
print PropertyReader().readProperty('source1_section','source_name1')
print PropertyReader().readProperty('source2_section','sn2_sc1_tb')
Content of .properties file:
[source1_section]
source_name1:module1
sn1_schema:schema1,schema2,schema3
sn1_sc1_tb:employee,department,location
sn1_sc2_tb:student,college,country
[source2_section]
source_name1:module2
sn2_schema:schema4,schema5,schema6
sn2_sc1_tb:employee,department,location
sn2_sc2_tb:student,college,country
You can try the python-dotenv library. This library reads key-value pairs from a .env (so not exactly a .properties file though) file and can set them as environment variables.
Here's a sample usage from the official documentation:
from dotenv import load_dotenv
load_dotenv() # take environment variables from .env.
# Code of your application, which uses environment variables (e.g. from `os.environ` or
# `os.getenv`) as if they came from the actual environment.