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Diffstat (limited to 'python.html.markdown')
| -rw-r--r-- | python.html.markdown | 40 |
1 files changed, 31 insertions, 9 deletions
diff --git a/python.html.markdown b/python.html.markdown index ace3f794..b939ebbe 100644 --- a/python.html.markdown +++ b/python.html.markdown @@ -14,7 +14,13 @@ executable pseudocode. Feedback would be highly appreciated! You can reach me at [@louiedinh](http://twitter.com/louiedinh) or louiedinh [at] [google's email service] Note: This article applies to Python 2.7 specifically, but should be applicable -to Python 2.x. For Python 3.x, take a look at the [Python 3 tutorial](http://learnxinyminutes.com/docs/python3/). +to Python 2.x. Python 2.7 is reachong end of life and will stop beeign maintained in 2020, +it is though recommended to start learnign Python with Python 3. +For Python 3.x, take a look at the [Python 3 tutorial](http://learnxinyminutes.com/docs/python3/). + +It is also possible to write Python code which is compatible with Python 2.7 and 3.x at the same time, +using Python [`__future__` imports](https://docs.python.org/2/library/__future__.html). `__future__` imports +allow you to write Python 3 code that will run on Python 2, so check out the Python 3 tutorial. ```python @@ -142,7 +148,13 @@ bool("") # => False #################################################### # Python has a print statement -print "I'm Python. Nice to meet you!" +print "I'm Python. Nice to meet you!" # => I'm Python. Nice to meet you! + +# Simple way to get input data from console +input_string_var = raw_input("Enter some data: ") # Returns the data as a string +input_var = input("Enter some data: ") # Evaluates the data as python code +# Warning: Caution is recommended for input() method usage +# Note: In python 3, input() is deprecated and raw_input() is renamed to input() # No need to declare variables before assigning to them. some_var = 5 # Convention is to use lower_case_with_underscores @@ -198,7 +210,7 @@ li[::-1] # => [3, 4, 2, 1] # Remove arbitrary elements from a list with "del" del li[2] # li is now [1, 2, 3] -r + # You can add lists li + other_li # => [1, 2, 3, 4, 5, 6] # Note: values for li and for other_li are not modified. @@ -327,8 +339,8 @@ prints: mouse is a mammal """ for animal in ["dog", "cat", "mouse"]: - # You can use % to interpolate formatted strings - print "%s is a mammal" % animal + # You can use {0} to interpolate formatted strings. (See above.) + print "{0} is a mammal".format(animal) """ "range(number)" returns a list of numbers @@ -379,7 +391,13 @@ except (TypeError, NameError): pass # Multiple exceptions can be handled together, if required. else: # Optional clause to the try/except block. Must follow all except blocks print "All good!" # Runs only if the code in try raises no exceptions +finally: # Execute under all circumstances + print "We can clean up resources here" +# Instead of try/finally to cleanup resources you can use a with statement +with open("myfile.txt") as f: + for line in f: + print line #################################################### ## 4. Functions @@ -387,7 +405,7 @@ else: # Optional clause to the try/except block. Must follow all except blocks # Use "def" to create new functions def add(x, y): - print "x is %s and y is %s" % (x, y) + print "x is {0} and y is {1}".format(x, y) return x + y # Return values with a return statement # Calling functions with parameters @@ -406,7 +424,7 @@ varargs(1, 2, 3) # => (1, 2, 3) # You can define functions that take a variable number of -# keyword args, as well, which will be interpreted as a map if you do not use ** +# keyword args, as well, which will be interpreted as a dict if you do not use ** def keyword_args(**kwargs): return kwargs @@ -467,9 +485,12 @@ add_10(3) # => 13 # There are also anonymous functions (lambda x: x > 2)(3) # => True +(lambda x, y: x ** 2 + y ** 2)(2, 1) # => 5 # There are built-in higher order functions map(add_10, [1, 2, 3]) # => [11, 12, 13] +map(max, [1, 2, 3], [4, 2, 1]) # => [4, 2, 3] + filter(lambda x: x > 5, [3, 4, 5, 6, 7]) # => [6, 7] # We can use list comprehensions for nice maps and filters @@ -497,7 +518,7 @@ class Human(object): # An instance method. All methods take "self" as the first argument def say(self, msg): - return "%s: %s" % (self.name, msg) + return "{0}: {1}".format(self.name, msg) # A class method is shared among all instances # They are called with the calling class as the first argument @@ -624,16 +645,17 @@ print say(say_please=True) # Can you buy me a beer? Please! 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