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other:python:misc_by_jyp [2021/08/16 14:18]
jypeter Added ordered dictionaries
other:python:misc_by_jyp [2021/10/26 11:42] (current)
jypeter [Sorting] Added content
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 <WRAP center round tip 60%> <WRAP center round tip 60%>
-You will find on this page some useful, but unsorted, python tips and tricks that can't fit in a section of the main [[other:​python:​jyp_steps|JYP'​s recommended steps for learning python]] page+You will find on this page some **useful, but unsorted, python tips and tricks** that can't fit in a section of the main [[other:​python:​jyp_steps|JYP'​s recommended steps for learning python]] page
 </​WRAP>​ </​WRAP>​
  
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     * [[https://​docs.python.org/​3/​library/​pathlib.html#​correspondence-to-tools-in-the-os-module|Matching pathlib, and os or os.path functions]]     * [[https://​docs.python.org/​3/​library/​pathlib.html#​correspondence-to-tools-in-the-os-module|Matching pathlib, and os or os.path functions]]
   * [[https://​docs.python.org/​3/​library/​shutil.html|High-level file operations]]   * [[https://​docs.python.org/​3/​library/​shutil.html|High-level file operations]]
 +
 +
 +=== Example: getting the full path of the Python used ===
 +
 +Note: the actual python may be different from the default python!
 +
 +<​code>​$ which python
 +/​usr/​bin/​python
 +
 +$ /​modfs/​modtools/​miniconda3//​envs/​analyse_3.6_test/​bin/​python
 +>>>​ import sys, shutil
 +>>>​ shutil.which('​python'​)
 +'/​usr/​bin/​python'​
 +>>>​ sys.executable
 +'/​modfs/​modtools/​miniconda3//​envs/​analyse_3.6_test/​bin/​python'</​code>​
 +
 +
 +=== Example: getting the full path of a script ===
 +
 +<​code>>>>​ import os
 +>>>​ os.getcwd()
 +'/​home/​jypmce/​PMIP4'​
 +>>>​ os.path.exists('​./​argv_test.py'​)
 +True
 +>>>​ os.path.abspath('​./​argv_test.py'​)
 +'/​home/​jypmce/​PMIP4/​argv_test.py'​
 +>>>​ os.path.exists('/​home/​jypmce/​PMIP4/​argv_test.py'​)
 +True
 +</​code>​
 +
  
 === Example: getting the size(s) of all the files in a directory === === Example: getting the size(s) of all the files in a directory ===
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 >>>​ sum(files_sizes) >>>​ sum(files_sizes)
 64792</​code>​ 64792</​code>​
 +
 +==== Generating file names ====
 +
 +=== Name depending on the current date/time ===
 +
 +<​code>>>>​ import time
 +>>>​ plot_version = time.strftime('​%Y%m%d_%H%M'​)
 +>>>​ f_name = '​test_%s.nc'​ % (plot_version,​)
 +>>>​ f_name
 +'​test_20210827_1334.nc'​
 +</​code>​
 +
 +=== Temporary file ===
 +
 +<​code>>>>​ import tempfile, os
 +>>>​ f_tmp = tempfile.NamedTemporaryFile(mode='​w',​ suffix='​.nc',​ delete=False)
 +>>>​ f_tmp
 +<​tempfile._TemporaryFileWrapper object at 0x2b5614743820>​
 +>>>​ f_tmp.name
 +'/​tmp/​tmpi6uk9hre.nc'​
 +>>>​ f_tmp.close()
 +>>>​ os.remove(f_tmp.name)</​code>​
 ==== Using command-line arguments ==== ==== Using command-line arguments ====
  
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 ==== Using ordered dictionaries ==== ==== Using ordered dictionaries ====
  
-Check the [[https://​realpython.com/​python-ordereddict/​|OrderedDict vs dict in Python: The Right Tool for the Job]] tutorial+**Dictionary order is guaranteed to be insertion order**! Note that the [[https://​docs.python.org/​3/​library/​stdtypes.html#​dict|usual Python dictionary]] also guarantees the order since version **3.6** 
 + 
 +Check the [[https://​docs.python.org/​3/​library/​collections.html#​collections.OrderedDict|OrderedDict class]] (''​from collections import OrderedDict''​) and the [[https://​realpython.com/​python-ordereddict/​|OrderedDict vs dict in Python: The Right Tool for the Job]] tutorial 
 + 
 +==== Printing a readable version of long lists or dictionaries ==== 
 + 
 +The [[https://​docs.python.org/​3/​library/​pprint.html|pprint]] module can be used for //pretty printing// objects (lists, dictionaries,​ ...). It will wrap long lines in a meaningful way 
 + 
 +<​code>>>>​ import pprint 
 + 
 +>>>​ test_dic = {'​AWI-ESM-1-1-LR_AWI':​{'​r1i1p1f1':​ {'​grid':​ '​gn'​}},​ '​CESM2_NCAR':​{'​r1i1p1f1':​ {'​grid':​ '​gn'​}},​ '​IPSL-CM6A-LR_IPSL':​{'​r1i1p1f1':​ {'​grid':​ '​gr'​},​ '​r1i1p1f2':​ {'​grid':​ '​gr'​},​ '​r1i1p1f3':​ {'​grid':​ '​gr'​},​ '​r1i1p1f4':​ {'​grid':​ '​gr'​}}} 
 + 
 +>>>​ print(test_dic) 
 +{'​AWI-ESM-1-1-LR_AWI':​ {'​r1i1p1f1':​ {'​grid':​ '​gn'​}},​ '​CESM2_NCAR':​ {'​r1i1p1f1':​ {'​grid':​ '​gn'​}},​ '​IPSL-CM6A-LR_IPSL':​ {'​r1i1p1f1':​ {'​grid':​ '​gr'​},​ '​r1i1p1f2':​ {'​grid':​ '​gr'​},​ '​r1i1p1f3':​ {'​grid':​ '​gr'​},​ '​r1i1p1f4':​ {'​grid':​ '​gr'​}}} 
 + 
 +>>>​ pprint.pprint(test_dic) 
 +{'​AWI-ESM-1-1-LR_AWI':​ {'​r1i1p1f1':​ {'​grid':​ '​gn'​}},​ 
 + '​CESM2_NCAR':​ {'​r1i1p1f1':​ {'​grid':​ '​gn'​}},​ 
 + '​IPSL-CM6A-LR_IPSL':​ {'​r1i1p1f1':​ {'​grid':​ '​gr'​},​ 
 +                       '​r1i1p1f2':​ {'​grid':​ '​gr'​},​ 
 +                       '​r1i1p1f3':​ {'​grid':​ '​gr'​},​ 
 +                       '​r1i1p1f4':​ {'​grid':​ '​gr'​}}} 
 +                        
 +>>>​ dir(test_dic) 
 +['​__class__',​ '​__contains__',​ '​__delattr__',​ [... lots of unreadable stuff removed...] '​setdefault',​ '​update',​ '​values'​] 
 + 
 +>>>​ pprint.pprint(dir(test_dic)) 
 +['​__class__',​ 
 + '​__contains__',​ 
 + 
 +[... lots of lines removed in this example ] 
 + 
 + '​setdefault',​ 
 + '​update',​ 
 + '​values'​] 
 + 
 +</​code>​ 
 + 
 +==== Sorting ==== 
 + 
 +  * [[https://​docs.python.org/​3/​howto/​sorting.html|Sorting HOW TO]] 
 +  * Example: sorting the keys and the values of a dictionary, and then using the ''​key''​ parameter to sort the keys of a dictionary according to the value associated with the key 
 +    * If we provide a ''​key''​ function, the ''​sort''​ function will sort the elements by the values returned by the function, instead of sorting by the initial values. The function used for generating the key below is very simple and we can use a //lambda// (i.e //in place//) function 
 +    * <​code>>>>​ demo_dic = {'​a':​10,​ '​b':​5,​ '​c':​-1,​ '​d':​0} 
 + 
 +>>>​ sorted(demo_dic.keys()) 
 +['​a',​ '​b',​ '​c',​ '​d'​] 
 + 
 +>>>​ sorted(demo_dic.values()) 
 +[-1, 0, 5, 10] 
 + 
 +>>>​ sorted(demo_dic.keys(),​ key=lambda key_name:​demo_dic[key_name]) 
 +['​c',​ '​d',​ '​b',​ '​a'​]</​code>​ 
  
 /* /*
other/python/misc_by_jyp.1629123525.txt.gz · Last modified: 2021/08/16 14:18 by jypeter