diff --git a/MANIFEST.in b/MANIFEST.in
index 6177c41..d18b373 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -4,3 +4,4 @@ include INSTALL.md
 include setup.py
 include tests/__init__.py
 include pypreprocessor/__init__.py
+include pypreprocessor/__main__.py
diff --git a/README.md b/README.md
index 281ca09..53aedbf 100644
--- a/README.md
+++ b/README.md
@@ -55,17 +55,16 @@
 
 ## Syntax
 
-The syntax for pypreprocessor uses a select subset of the stanard c-style preprocessor directives, and then some...
+The syntax for pypreprocessor uses a select subset of the standard c-style preprocessor directives, and then some...
 
 **Supported directives**
 
-* define non-value constants used by the preprocessor
+* defines constants (valued or not) used by the preprocessor
 ```python
-#define constant
+#define constant [value]
 ```
 
-
-* remove a non-value constant from the list of defined constants
+* removes a constant from the list of defined constants
 ```python
 #undef constant
 ```
@@ -75,21 +74,46 @@ The syntax for pypreprocessor uses a select subset of the stanard c-style prepro
 #ifdef constant
 ```
 
-* makes the subsequent block of code available if all of the preceding #ifdef statements return false
+* makes the subsequent block of code available if the specified constant is not set
+```python
+#ifndef constant
+```
+
+* makes the subsequent block of code available if the specified condition returns true
+```python
+#if boolean_condition
+```
+
+* makes the subsequent block of code available if all of the preceding #ifdef, #elif, #if statements returns false
 ```python
 #else
 ```
 
+* makes the subsequent block of code available if all of the preceding #ifdef, #elif, #if statements return false and the specifified condition returns true
+```python
+#elif boolean_condition
+```
+
 * required to close out an #ifdef/#else block
 ```python
 #endif
 ```
+
+* Interrupts execution and returns error when reached
+```python
+#error
+```
+
+**Unofficial supported directives**
+
+Unofficial directives exist to ease writing long files but should not be used in file that could be preprocessed without pypreprocessor 
+
 * possibility to close all open blocks
 ```python
 #endifall
 ```
 
-* exclude the subsequent block of code (conditionals not included). I know it doesn't fit into the standard set of c-style directives but it's too handy to exclude (no pun).
+* excludes the subsequent block of code (conditionals not included). I know it doesn't fit into the standard set of c-style directives but it's too handy to exclude (no pun).
 ```python
 #exclude
 ```
@@ -99,6 +123,50 @@ The syntax for pypreprocessor uses a select subset of the stanard c-style prepro
 #endexclude
 ```
 
+* Attempts closing <num> #ifdef/#else blocks
+```python
+#endif<num>
+```
+
+* Similar to #ifndef
+```python
+#ifnotdef constant
+```
+
+* Similar to #ifndef
+```python
+#ifdefnot constant
+```
+
+* Similar to #elif boolean_condition
+```python
+#elseif boolean_condition
+```
+
+* Similar to #elif constant
+```python
+#elseifdef constant
+```
+
+* Similar to #endif followed by #ifdef constant
+```python
+#endififdef constant
+```
+
+**Unsupported directives**
+
+Unsupported directives are not handled by pypreprocessor and concidered as comment
+
+* Inserts a particuliar header from another file. This has no use in Python
+```python
+#include
+```
+
+* Issues special commands to the compiler, using a standardized method. This has no use in Python
+```python
+#pragma
+```
+
 **Options**
 
 The following options need to be set prior to pypreprocessor.parse()
@@ -113,12 +181,16 @@ add defines to the preprocessor programmatically, this allows the source file to
 pypreprocessor.run = True / False
 pypreprocessor.resume = True / False
 pypreprocessor.save = True / False
+pypreprocessor.overload = True / False
+pypreprocessor.quiet = True / False
 ```
 set the options of the preprocessor:
 
 * run: Run the preprocessed code if true. Default is true
 * resume: Return after a file is preprocessed and can preprocess a next file if true. Default is false
 * save: Save preprocessed code if true. Default is true
+* overload: Any defines added to the preprocessor will overload existing defines. Default is false
+* quiet: no warning about not understood directives or missing #indef
 
 ```python
 pypreprocessor.input = 'inputFile.py'
diff --git a/pypreprocessor/__init__.py b/pypreprocessor/__init__.py
index b0b2a07..4c5371e 100644
--- a/pypreprocessor/__init__.py
+++ b/pypreprocessor/__init__.py
@@ -2,20 +2,38 @@
 # pypreprocessor.py
 
 __author__ = 'Evan Plaice'
-__coauthor__ = 'Hendi O L, Epikem'
-__version__ = '0.7.7'
+__coauthor__ = 'Hendi O L, Epikem, Laurent Pinson'
+__version__ = '1.0'
 
 import sys
 import os
 import traceback
 import imp
 import io
+import collections
+import re
+
+#support for <=0.7.7
+class customDict(dict):
+    def append(self, var):
+        self[var]=True
+
+
 class preprocessor:
-    def __init__(self, inFile=sys.argv[0], outFile='', defines=[], \
-            removeMeta=False, escapeChar=None, mode=None, escape='#', \
-            run=True, resume=False, save=True):
+    __overloaded = []
+    defines = customDict()
+
+    def __init__(self, inFile=sys.argv[0], outFile='', defines={}, removeMeta=False, 
+                 escapeChar=None, mode=None, escape='#', run=True, resume=False, 
+                 save=True, overload=True, quiet=False):
         # public variables
-        self.defines = defines
+        # support for <=0.7.7
+        if isinstance(defines, collections.Sequence):
+            for x in defines:
+                self.define(*x.split(':'))
+        else:
+            for x,y in defines.items():
+                self.define(x,y)
         self.input = inFile
         self.output = outFile
         self.removeMeta = removeMeta
@@ -25,26 +43,30 @@ def __init__(self, inFile=sys.argv[0], outFile='', defines=[], \
         self.run = run
         self.resume = resume
         self.save = save
-        self.readEncoding = sys.stdin.encoding
+        self.overload = overload
+        self.quiet = quiet
+        self.readEncoding = sys.stdin.encoding 
         self.writeEncoding = sys.stdout.encoding
+
         # private variables
-        self.__linenum = 0
-        self.__excludeblock = False
-        self.__ifblocks = []
-        self.__ifconditions = []
-        self.__evalsquelch = True
-        self.__outputBuffer = ''
+        self.__reset_internal()
 
     def check_deprecation(self):
+        """
+            Deprecation checks for older implementation of this library
+        
+        """
         def deprecation(message):
             import warnings
             warnings.simplefilter('always', DeprecationWarning)
             warnings.warn(message, DeprecationWarning)
             warnings.simplefilter('default', DeprecationWarning)
+
         if self.escapeChar != None:
             deprecation("'pypreprocessor.escapeChar' is deprecated. Use 'escape' instead.")
             if self.escape == '#':
                 self.escape = self.escapeChar
+
         if self.mode != None:
             msg = "'pypreprocessor.mode' is deprecated. Use 'run/resume/save' options instead."
             if self.run != True or self.resume != False or self.save != True:
@@ -66,220 +88,314 @@ def deprecation(message):
                     print('Unknown mode : ' + str(self.mode))
             deprecation(msg)
 
-    # reseting internal things to parse a second file
     def __reset_internal(self):
         self.__linenum = 0
         self.__excludeblock = False
-        self.__ifblocks = []
-        self.__ifconditions = []
-        self.__evalsquelch = True
+        # contains the evaluated if conditions
+        # due to the introduction of #elif, elements of __ifblocks are duos of boolean
+        # the 1st is the evaluation of the current #if or #elif or #else
+        # the 2nd indicates if at least one #if or #elif was True in the whole #if/#endif block
+        self.__ifblocks = []  
+        # contains the if conditions
+        self.__ifconditions = [] 
         self.__outputBuffer = ''
+        self.__overloaded = list(self.defines.keys()) if self.overload else []
+
+    def define(self, name, val=True):
+        """
+            Adds variable definition to the store as expected from a #define directive.
+            The directive can contains no value as it would be tested with a #ifdef directive or 
+            with a value for an evaluation as in an #if directive.
 
-    # the #define directive
-    def define(self, define):
-        self.defines.append(define)
+            Note: if the `name` was part of the initial definition and `overload` was set to 
+            True, this new definition will be skipped
+        
+        :params
+            name (str): definition name
+            
+            val (str): definition value when it exists. Default is None
+        """
+        # try conversion for number else evaluate() might fail
+        try:
+            val = int(val)
+        except:
+            # assume val is string 
+            pass    
+        if name not in self.__overloaded:
+            self.defines[name]=val
 
-    # the #undef directive
     def undefine(self, define):
-        # re-map the defines list excluding the define specified in the args
-        self.defines[:] = [x for x in self.defines if x != define]
+        """
+            Removes variable definition from store as expected from an #undef directive
 
-    # search: if define is defined
-    def search_defines(self, define):
+        :params
+            define (str): definition name
+            
+        """
         if define in self.defines:
+            self.defines.pop(define)
+
+    def __is_defined(self, define):
+        """
+            Checks variable is defined as used in #ifdef, #ifnotdef & #elseif directives
+
+        :params
+            define (str): definition name
+            
+        """
+        return define in self.defines
+
+    def __evaluate_if(self, line):
+        """
+            Evaluate the content of a #if, #elseif, #elif directive
+
+        :params
+            line (str): definition name
+            
+        """
+        try:
+            # replace C-style bool format by Python's
+            line = line.replace('&&', 'and').replace('||', 'or').replace('!','not ')
+            return eval(line, self.defines) or False
+        except BaseException as e:
+            print(str(e))
+            self.exit_error(self.escape + 'if')
+
+    def __validate_ifs(self):
+        """
+            Evaluate if the successive #ifs block are validated for the current position
+
+        :return
+            ifs (bool): True if all ifs condition are validated
+
+        """
+        # no ifs mean we pass else check all ifs are True
+        return not self.__ifblocks or all(x[0] for x in self.__ifblocks)
+
+    def __is_directive(self, line, directive, *size):
+        """
+            Checks the `line` is a `directive` and , if `size` is provided, checks its number of 
+            elements is amongst the list of allowed `size` 
+
+        :params:
+            line (str): line to check
+
+            directive (str): directive to be found in the `line`
+
+            *size (int): list of allowed number of elements to compose the directive. Can be empty
+        
+        """
+        if line.startswith(self.escape + directive):
+            if size and len(line.split()) not in size:
+                self.exit_error(self.escape + directive)
             return True
-        else:
-            return False
+        return False
+
+    def __cleanup_line(self, line):
+        """
+            Clean a line of anything that should not impact parsing such as C-style comment
+
+        :params:
+            line (str): line to check
 
-    #returning: validness of #ifdef #else block
-    def __if(self):
-        value = bool(self.__ifblocks)
-        for ib in self.__ifblocks:
-            value *= ib   #* represents and: value = value and ib
-        return not value    #not: because True means removing
+        :return
+            line (str): cleaned line
+        
+        """
+        line= re.sub('\s*/\*.*\*/\s+', '', line) #remove /* */ C-style comment
+        line= re.sub('\s*//.*', '', line) #remove // C-style comment
+        return line
 
-    # evaluate
     def lexer(self, line):
-    # return values are (squelch, metadata)
+        """
+            Analyse the `line`. This method attempts to find a known directive and, when found, to 
+            understand it and to perform appropriate action.
+
+        :params
+            line (str): line of code to analyse
+
+        :return
+            exclude (bool): should the line be excluded in the final output?
+
+            metadata (bool): is this line a directive?
+
+        """
+        line = line.strip()
         if not (self.__ifblocks or self.__excludeblock):
             if 'pypreprocessor.parse()' in line:
                 return True, True
-            #this block only for faster processing (not necessary)
-            elif line[:len(self.escape)] != self.escape:
-                return False, False
-        # handle #define directives
-        if line[:len(self.escape) + 6] == self.escape + 'define':
-            if len(line.split()) != 2:
-                self.exit_error(self.escape + 'define')
-            else:
-                self.define(line.split()[1])
-                return False, True
-        # handle #undef directives
-        elif line[:len(self.escape) + 5] == self.escape + 'undef':
-            if len(line.split()) != 2:
-                self.exit_error(self.escape + 'undef')
-            else:
-                self.undefine(line.split()[1])
-                return False, True
-        # handle #exclude directives
-        elif line[:len(self.escape) + 7] == self.escape + 'exclude':
-            if len(line.split()) != 1:
-                self.exit_error(self.escape + 'exclude')
-            else:
-                self.__excludeblock = True
-                return False, True
-        # handle #endexclude directives
-        elif line[:len(self.escape) + 10] == self.escape + 'endexclude':
-            if len(line.split()) != 1:
-                self.exit_error(self.escape + 'endexclude')
-            else:
-                self.__excludeblock = False
-                return False, True
-        # handle #ifnotdef directives (is the same as: #ifdef X #else)
-        elif line[:len(self.escape) + 8] == self.escape + 'ifdefnot':
-            if len(line.split()) != 2:
-                self.exit_error(self.escape + 'ifdefnot')
-            else:
-                self.__ifblocks.append(not self.search_defines(line.split()[1]))
-                self.__ifconditions.append(line.split()[1])
-                return False, True
-        # handle #ifdef directives
-        elif line[:len(self.escape) + 5] == self.escape + 'ifdef':
-            if len(line.split()) != 2:
-                self.exit_error(self.escape + 'ifdef')
-            else:
-                self.__ifblocks.append(self.search_defines(line.split()[1]))
-                self.__ifconditions.append(line.split()[1])
-                return False, True
-        # handle #else...
-        # handle #elseif directives
-        elif line[:len(self.escape) + 6] == self.escape + 'elseif':
-            if len(line.split()) != 2:
-                self.exit_error(self.escape + 'elseif')
-            else:
-                self.__ifblocks[-1] = not self.__ifblocks[-1]
-                  #self.search_defines(self.__ifconditions[-1]))
-                self.__ifblocks.append(self.search_defines(line.split()[1]))
-                self.__ifconditions.append(line.split()[1])
-            return False, True
-        # handle #else directives
-        elif line[:len(self.escape) + 4] == self.escape + 'else':
-            if len(line.split()) != 1:
-                self.exit_error(self.escape + 'else')
-            else:
-                self.__ifblocks[-1] = not self.__ifblocks[-1]
-                  #self.search_defines(self.__ifconditions[-1]))
-            return False, True
-        # handle #endif..
-        # handle #endififdef
-        elif line[:len(self.escape) + 10] == self.escape + 'endififdef':
-            if len(line.split()) != 2:
-                self.exit_error(self.escape + 'endififdef')
+
+        # put that block here for faster processing
+        if not line.startswith(self.escape): #No directive --> execute
+            # exclude=True if we are in an exclude block or the ifs are not validated
+            return self.__excludeblock or not self.__validate_ifs(), False
+
+        # strip line of any C-style comment
+        line = self.__cleanup_line(line)
+
+        if self.__is_directive(line, 'define', 2,3):
+            self.define(*line.split()[1:])
+
+        elif self.__is_directive(line, 'undef', 2):
+            self.undefine(line.split()[1])
+
+        elif self.__is_directive(line, 'exclude', 1):
+            self.__excludeblock = True
+
+        elif self.__is_directive(line, 'endexclude', 1):
+            self.__excludeblock = False
+
+        # #ifnotdef sounds better than #ifdefnot..
+        elif self.__is_directive(line, 'ifdefnot', 2) or \
+        self.__is_directive(line, 'ifnotdef', 2) or \
+        self.__is_directive(line, 'ifndef', 2):
+            _check = not self.__is_defined(line.split()[1])
+            self.__ifblocks.append([ _check, _check])
+            self.__ifconditions.append(line.split()[1])
+
+        elif self.__is_directive(line, 'ifdef', 2):
+            _check = self.__is_defined(line.split()[1])
+            self.__ifblocks.append([ _check, _check])
+            self.__ifconditions.append(line.split()[1])
+
+        elif self.__is_directive(line, 'if'):
+            _check = self.__evaluate_if(' '.join(line.split()[1:]))
+            self.__ifblocks.append([ _check, _check])
+            self.__ifconditions.append(' '.join(line.split()[1:]))
+
+        # since in version <=0.7.7, it didn't handle #if it should be #elseifdef instead.
+        # kept elseif with 2 elements for retro-compatibility (equivalent to #elseifdef).
+        elif self.__is_directive(line, 'elseif') or \
+        self.__is_directive(line, 'elif'):
+            _cur, _whole = self.__ifblocks[-1]
+            if len(line.split()) == 2:
+                #old behaviour
+                _check = self.__is_defined(line.split()[1])
             else:
-                if len(self.__ifconditions) >= 1:
+                #new behaviour
+                _check = self.__evaluate_if(' '.join(line.split()[1:]))
+            self.__ifblocks[-1]=[ not _whole and _check, _whole or _check ]
+            self.__ifconditions[-1]=' '.join(line.split()[1:])
+
+        elif self.__is_directive(line, 'elseifdef', 2):
+            _cur, _whole = self.__ifblocks[-1]
+            _check = self.__is_defined(line.split()[1])
+            self.__ifblocks[-1]=[ not _whole and _check, _whole or _check ]
+            self.__ifconditions[-1]=' '.join(line.split()[1:])
+
+        elif self.__is_directive(line, 'else', 1):
+            _cur, _whole = self.__ifblocks[-1]
+            self.__ifblocks[-1] = [not _whole, not _whole] #opposite of the whole if/elif block
+
+        elif self.__is_directive(line, 'endififdef', 2):
+            # do endif
+            if len(self.__ifconditions) >= 1:
+                self.__ifblocks.pop(-1)
+                self.__ifconditions.pop(-1)
+            # do ifdef
+            self.__ifblocks.append(self.__is_defined(line.split()[1]))
+            self.__ifconditions.append(line.split()[1])
+
+        elif self.__is_directive(line, 'endifall', 1):
+            self.__ifblocks = []
+            self.__ifconditions = []
+
+        # handle #endif and #endif<numb> directives
+        elif self.__is_directive(line, 'endif', 1):
+            try:
+                number = int(line[6:])
+            except ValueError as VE:
+                number = 1
+
+            try:
+                while number:
                     self.__ifblocks.pop(-1)
-                    self.__ifcondition = self.__ifconditions.pop(-1)
-                else:
-                    self.__ifblocks = []
-                    self.__ifconditions = []
-                self.__ifblocks.append(self.search_defines(line.split()[1]))
-                self.__ifconditions.append(line.split()[1])
-                return False, True
-        # handle #endifall directives
-        elif line[:len(self.escape) + 8] == self.escape + 'endifall':
-            if len(line.split()) != 1:
-                self.exit_error(self.escape + 'endifall')
-            else:
-                self.__ifblocks = []
-                self.__ifconditions = []
-                return False, True
-        # handle #endif and #endif numb directives
-        elif line[:len(self.escape) + 5] == self.escape + 'endif':
-            if len(line.split()) != 1:
-                self.exit_error(self.escape + 'endif number')
-            else:
-                try:
-                    number = int(line[6:])
-                except ValueError as VE:
-                    #print('ValueError',VE)
-                    #self.exit_error(self.escape + 'endif number')
-                    number = 1
-                if len(self.__ifconditions) > number:
-                    for i in range(0, number):
-                        self.__ifblocks.pop(-1)
-                        self.__ifcondition = self.__ifconditions.pop(-1)
-                elif len(self.__ifconditions) == number:
-                    self.__ifblocks = []
-                    self.__ifconditions = []
-                else:
-                    print('Warning try to remove more blocks than present', \
-                      self.input, self.__linenum)
-                    self.__ifblocks = []
-                    self.__ifconditions = []
-                return False, True
-        else: #No directive --> execute
-            # process the excludeblock
-            if self.__excludeblock is True:
-                return True, False
-            # process the ifblock
-            elif self.__ifblocks: # is True:
-                return self.__if(), False
-            #here can add other stuff for deleting comnments eg
-            else:
-                return False, False
+                    self.__ifconditions.pop(-1)
+                    number-=1
+            except:
+                if not self.quiet:
+                    print('Warning trying to remove more blocks than present', 
+                          self.input, self.__linenum)
+
+        elif self.__is_directive(line, 'error'):
+            if self.__validate_ifs():
+                print('File: "' + self.input + '", line ' + str(self.__linenum + 1))
+                print('Error directive reached')
+                sys.exit(1)
+
+        else: 
+            # escapechar + space ==> comment
+            # starts with #!/ ==> shebang
+            # else print warning
+            if len(line.split()[0]) > 1 and not line.startswith('#!/') and not self.quiet:
+                print('Warning unknown directive or comment starting with ', 
+                        line.split()[0], self.input, self.__linenum + 1)
+
+        return False, True
 
     # error handling
     def exit_error(self, directive):
-        print('File: "' + self.input + '", line ' + str(self.__linenum))
+        """
+            Prints error and interrupts execution
+
+        :params
+            directive (str): faulty directive
+            
+        """
+        print('File: "' + self.input + '", line ' + str(self.__linenum + 1))
         print('SyntaxError: Invalid ' + directive + ' directive')
         sys.exit(1)
+
     def rewrite_traceback(self):
+        """
+            Dumps traceback but with the input file name included
+
+        """
         trace = traceback.format_exc().splitlines()
-        index = 0
+        trace[-2]=trace[-2].replace("<string>", self.input)
         for line in trace:
-            if index == (len(trace) - 2):
-                print(line.replace("<string>", self.input))
-            else:
-                print(line)
-            index += 1
+            print(line)
 
-    # parsing/processing
     def parse(self):
+        """
+            Main method:
+            - reset internal counters/values
+            - check & warn about deprecation
+            - starts the parsing of the input file
+            - warn of unclosed #ifdef blocks if any
+            - trigger post-process activities
+
+        """
         self.__reset_internal()
         self.check_deprecation()
         # open the input file
-        input_file = io.open(os.path.join(self.input), 'r', encoding=self.readEncoding)
         try:
-            # process the input file
-            for line in input_file:
-                self.__linenum += 1
-                # to squelch or not to squelch
-                squelch, metaData = self.lexer(line)
-                # process and output
-                if self.removeMeta is True:
-                    if metaData is True or squelch is True:
+            with io.open(os.path.join(self.input), 'r', encoding=self.readEncoding) as input_file:
+                for self.__linenum, line in enumerate(input_file):
+                    exclude, metaData = self.lexer(line)
+                    # process and output
+                    if self.removeMeta:
+                        if metaData or exclude:
+                            continue
+                    if exclude:
+                        if metaData:
+                            self.__outputBuffer += self.escape + line
+                        else:
+                            self.__outputBuffer += self.escape[0] + line
                         continue
-                if squelch is True:
-                    if metaData:
-                        self.__outputBuffer += self.escape + line
                     else:
-                        self.__outputBuffer += self.escape[0] + line
-                    continue
-                if squelch is False:
-                    self.__outputBuffer += line
-                    continue
+                        self.__outputBuffer += line
+                        continue
         finally:
-            input_file.close()
             #Warnings for unclosed #ifdef blocks
-            if self.__ifblocks:
+            if self.__ifblocks and not self.quiet:
                 print('Warning: Number of unclosed Ifdefblocks: ', len(self.__ifblocks))
                 print('Can cause unwished behaviour in the preprocessed code, preprocessor is safe')
                 try:
                     select = input('Do you want more Information? ')
                 except SyntaxError:
                     select = 'no'
-                select = select.lower()
-                if select in ('yes', 'true', 'y', '1'):
+                if select.lower() in ('yes', 'true', 'y', '1'):
                     print('Name of input and output file: ', self.input, ' ', self.output)
                     for i, item in enumerate(self.__ifconditions):
                         if (item in self.defines) != self.__ifblocks[i]:
@@ -289,18 +405,25 @@ def parse(self):
                         print('Block:', item, ' is in condition: ', cond)
         self.post_process()
 
-    # post-processor
     def post_process(self):
+        """
+            Perform post-parsing activities:
+            - write output file from parsing.
+            - override import if requested or attempt execution with its content
+            - remove output file if no save was requested
+            - force exit if resume was not requested
+
+        """
         try:
             # set file name
-            if self.output == '':
+            if not self.output:
                 self.output = self.input[0:-len(self.input.split('.')[-1])-1]+'_out.'+self.input.split('.')[-1]
-            # open file for output
-            output_file = io.open(self.output, 'w', encoding=self.writeEncoding)
+
             # write post-processed code to file
-            output_file.write(self.__outputBuffer)
+            with io.open(self.output, 'w', encoding=self.writeEncoding) as output_file:
+                output_file.write(self.__outputBuffer)
         finally:
-            output_file.close()
+            pass
 
         if self.run:
             # if this module is loaded as a library override the import
@@ -308,10 +431,12 @@ def post_process(self):
                 self.override_import()
             else:
                 self.on_the_fly()
+
         if not self.save:
             # remove tmp file
             if os.path.exists(self.output):
                 os.remove(self.output)
+
         if not self.resume:
             # break execution so python doesn't
             # run the rest of the pre-processed code
@@ -319,6 +444,10 @@ def post_process(self):
 
     # postprocessor - override an import
     def override_import(self):
+        """
+            Override the import of the output of the processed file
+
+        """
         try:
             moduleName = self.input.split('.')[0]
             tmpModuleName = self.output.split('.')[0]
@@ -334,10 +463,13 @@ def override_import(self):
 
     # postprocessor - on-the-fly execution
     def on_the_fly(self):
+        """
+            Execute output of the processed file
+
+        """
         try:
-            f = io.open(self.output, "r", encoding=self.readEncoding)
-            exec(f.read())
-            f.close()
+            with io.open(self.output, "r", encoding=self.readEncoding) as f:
+                exec(f.read())
         except:
             self.rewrite_traceback()
 
diff --git a/pypreprocessor/__main__.py b/pypreprocessor/__main__.py
new file mode 100644
index 0000000..73235b2
--- /dev/null
+++ b/pypreprocessor/__main__.py
@@ -0,0 +1,34 @@
+import argparse
+from . import preprocessor
+
+parser = argparse.ArgumentParser(
+    description="Check https://github.com/interpreters/pypreprocessor for documentation",
+    epilog="""Examples:
+    python -m """+__package__+""" somepython.py post-proc.py -m -d DEBUG FILE:4 EXEC
+    python -m """+__package__+""" table.json --escape #@ -d NUM:4 ID:1 
+    """,
+    formatter_class=argparse.RawDescriptionHelpFormatter,
+    usage=' python -m '+__package__+' input [output] [-h] [-r] [-m] [-e ESCAPE] [-o] [-q] [-d [DEFINE ...]]',
+)
+parser.add_argument("-r", "--run", help="run on the fly", 
+                    action='store_true', default=False)
+parser.add_argument("-m", "--removeMeta", help="remove meta lines from the output", 
+                    action='store_true', default=False)
+parser.add_argument("-e", "--escape", help="define the escape sequence to use. Default is #")
+parser.add_argument("-d", "--define", help="list of constants to define", nargs='*', default=[])
+parser.add_argument("-o", "--overload", help="overload variable definition in the file by those \
+                    provided by --define", action='store_true', default=False)
+parser.add_argument("-q", "--quiet", help="No warning on not understood directives and missign ending",
+                    action='store_true', default=False)
+parser.add_argument("input", help="input file.")
+parser.add_argument("output", nargs='?', help="output file. Default is <input_basename>_out.<input_extension>")
+args = parser.parse_args()
+
+p=preprocessor(inFile=args.input, defines=args.define, mode=None, removeMeta=args.removeMeta, escapeChar=None, 
+               run=args.run, resume=False, save=True, overload=args.overload, quiet=args.quiet)
+if args.output:
+    p.output = args.output
+if args.escape:
+    p.escape = args.escape
+
+p.parse()
\ No newline at end of file