Reformatting code with black instead of yapf

.flake8

@@ -0,0 +1,6 @@
+# Adopted from *Black*'s config
+
+[flake8]
+ignore = E203, E266, E501, W503
+max-line-length = 88
+select = B,C,E,F,W,T4,B9

.travis.yml

@@ -25,8 +25,8 @@ matrix:
       env: LINT=1
       script:
         - export PATH="$HOME/miniconda/bin:$PATH"
-        - yapf -dr modin/pandas
-        - flake8 --max-line-length=88 .
+        - black --check modin/
+        - flake8 .
 
 install:
   - ./.travis/install-dependencies.sh

.travis/install-dependencies.sh

@@ -46,12 +46,13 @@ elif [[ "$LINT" == "1" ]]; then
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
   conda install -y python==3.6.5
+  pip install black flake8 flake8-comprehensions
 
 else
   echo "Unrecognized environment."
   exit 1
 fi
 
 pip install -r requirements.txt
-pip install -q pytest flake8 flake8-comprehensions yapf feather-format lxml openpyxl xlrd numpy
+pip install -q pytest feather-format lxml openpyxl xlrd numpy
 

README.rst

@@ -7,6 +7,8 @@ Modin
 .. image:: https://readthedocs.org/projects/modin/badge/?version=latest
     :target: https://modin.readthedocs.io/en/latest/?badge=latest
 
+.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
+    :target: https://github.com/ambv/black
 |
 
 *Modin is a library for unifying the way you interact with your data*

modin/__init__.py

@@ -6,19 +6,18 @@ def git_version():
     def _execute_cmd_in_temp_env(cmd):
         # construct environment
         env = {}
-        for k in ['SYSTEMROOT', 'PATH', 'HOME']:
+        for k in ["SYSTEMROOT", "PATH", "HOME"]:
             v = os.environ.get(k)
             if v is not None:
                 env[k] = v
         # LANGUAGE is used on win32
-        env['LANGUAGE'] = 'C'
-        env['LANG'] = 'C'
-        env['LC_ALL'] = 'C'
-        return subprocess.Popen(
-            cmd, stdout=subprocess.PIPE, env=env).communicate()[0]
+        env["LANGUAGE"] = "C"
+        env["LANG"] = "C"
+        env["LC_ALL"] = "C"
+        return subprocess.Popen(cmd, stdout=subprocess.PIPE, env=env).communicate()[0]
 
     try:
-        git_revision = _execute_cmd_in_temp_env(['git', 'rev-parse', 'HEAD'])
+        git_revision = _execute_cmd_in_temp_env(["git", "rev-parse", "HEAD"])
         return git_revision.strip().decode()
     except OSError:
         return "Unknown"