PyCon Ireland 2013: Beautiful python code

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MAKING BEAUTIFUL PYTHON CODE Or Readability Counts JAIME BUELTA BY Thursday 17 October 13

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Developers like Python because code is beautiful Thursday 17 October 13

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Almost no one will appreciate it Thursday 17 October 13

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(At least until there’s a problem) Thursday 17 October 13

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BOSS DOES NOT CARE worried about costs and stuff Thursday 17 October 13

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CUSTOMERS DON’T CARE worried about functionality and stuff Thursday 17 October 13

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but your team will care Thursday 17 October 13

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most of the time, the effort difference between good code and bad code is small Thursday 17 October 13

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MY DREAM Thursday 17 October 13

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Thursday 17 October 13

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Thursday 17 October 13

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Thursday 17 October 13

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Thursday 17 October 13

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Thursday 17 October 13

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CODE IS ALWAYS CHANGING Thursday 17 October 13

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CODE NEEDS TO WORK Thursday 17 October 13

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“There's a difference between getting your hands dirty and being dirty.” DS Justin Ripley Thursday 17 October 13

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“There's a difference between getting your hands dirty and being dirty.” DS Justin Ripley (yes, the picture is not from Luther, but from The Good Cop) Thursday 17 October 13

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WHAT MAKES BEAUTIFUL CODE? Thursday 17 October 13

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EASY TO UNDERSTAND Thursday 17 October 13

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(THEREFORE, EASY TO CHANGE) Thursday 17 October 13

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NOT THE OTHER WAY AROUND Thursday 17 October 13

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OVERDESIGN Thursday 17 October 13

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GOOD CODE Thursday 17 October 13

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FITS IN YOUR HEAD Thursday 17 October 13

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BAD CODE... Thursday 17 October 13

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Thursday 17 October 13

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Thursday 17 October 13

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Function Thursday 17 October 13

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Function Module Thursday 17 October 13

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Function Module System Thursday 17 October 13

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Show how good you are HERE Not here Thursday 17 October 13

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Thursday 17 October 13

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Thursday 17 October 13

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LOCALITY CONSISTENCY VERBOSITY Thursday 17 October 13

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CONSISTENCY VERBOSITY Keep related stuff together LOCALITY Thursday 17 October 13

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LOCALITY VERBOSITY Use patterns CONSISTENCY Thursday 17 October 13

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LOCALITY CONSISTENCY When in doubt, explain VERBOSITY Thursday 17 October 13

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Be as OBVIOUS as possible in other words... Thursday 17 October 13

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LOCALITY Thursday 17 October 13

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MSG_TEMPLATE = ‘Template {date}: {msg}’ MORE_CONSTANTS... .... def log_msg(message): formatted_msg = MSG_TEMPLATE.format( date=utcnow(), msg=this_message ) print formatted_msg Thursday 17 October 13

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def log_msg(message): MSG_TEMPLATE = ‘{date}: {msg}’ formatted_msg = MSG_TEMPLATE.format( date=utcnow(), msg=message ) print formatted_msg Thursday 17 October 13

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MSG_TEMPLATE = ‘{date}: {msg}’ def log_msg(message): formatted_msg = TEMPLATE.format( date=utcnow(), msg=message ) print formatted_msg Thursday 17 October 13

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Related classes on the same module Function used only in a module not in independent module Keep ﬁles short Avoid boilerplate Separated business logic Thursday 17 October 13

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CONSISTENCY Thursday 17 October 13

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Humans are amazing recognizing patterns (so good we tend to see too many) Thursday 17 October 13

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PEP8 IS THE MOST IMPORTANT PATTERN COLLECTION OUT THERE Thursday 17 October 13

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Abstract common operations List comprehensions Decorators and with statement No private methods No getters and setters Thursday 17 October 13

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I LOVE MY BRICK! syndrome Thursday 17 October 13

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VERBOSITY Thursday 17 October 13

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data = "+RESP:GTTRI,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,"\ "%s,%s,%s,%s,%s,%s,%s\0" % (imei, number, reserved_1, reserved_2, gps_fix, speed, heading, altitude, gps_accuracy, longitude, latitude, send_time, mcc, mnc, lac, cellid, ta, count_num, ver) Thursday 17 October 13

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data = (‘+RESP:GTTRI,{imei},{number},{reserved_1},’ ‘{reserved_2},{gps_fix},{speed},{heading},’ ‘{altitude},{gps_accuracy},{longitude},’ ‘{latitude},{send_time}, {mmc}, {lac}, {cellid}’ ‘{ta},{count_num}, {version}’).format( imei=imei, number=number, reserved_1=reserved_1, reserved_2=reserved_2, gps_fix=gps_fix, speed=speed, heading=heading, altitude=altitude, gps_accuracy=gps_accuracy, longitude=longitude, latitude=latitude, send_time=send_time, mcc=mcc, mnc=mnc, lac=lac, cellid=cellid, ta=ta, count_num=count_num, version=ver, ) Thursday 17 October 13

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WHEN IN DOUBT, COMMENT Thursday 17 October 13

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PUTTING ALL TOGETHER Thursday 17 October 13

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results = [] for row in query_results: tag, value, updated = row if value and updated > last_time: TEMP = ‘tag: {0}, value: {1} result = TEMP.format(tag, value) results.append(result) Thursday 17 October 13

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def format_result(row): tag, value, _ = row TEMP = ‘tag: {0}, value: {1}’ return TEMP.format(tag, value) def interesting(row): _, value, updated = row return value and updated > last_time results = [format_result(row) for row in query_results if interesting(row)] Thursday 17 October 13

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SMART IS THE ENEMY OF READABILITY Thursday 17 October 13

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HAVE A GOOD REASON TO BE SMART And comment accordingly Thursday 17 October 13

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ONE DAY, SOMEONE WILL BE SURPRISED WITH YOUR CODE Thursday 17 October 13

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YOURSELF!!! Thursday 17 October 13

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SO, REMEMBER Thursday 17 October 13

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Thursday 17 October 13

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BE OBVIOUS Thursday 17 October 13

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ASSUME YOU CAN’T FIT A LOT OF CODE ON YOUR HEAD Thursday 17 October 13

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BE SMART IN SYSTEMS, NOT IN FUNCTIONS Thursday 17 October 13

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LOCALITY CONSISTENCY VERBOSITY Thursday 17 October 13

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Tell your buddies how much you appreciate them writing simple code! Thursday 17 October 13

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Thursday 17 October 13