nanotech example - v4.software-carpentry.org · sets and dictionaries nanotech example. how many...

Nanotech Example

Sets and Dictionaries

Nanotech Example

This work is licensed under the Creative Commons Attribution License

See http://software-carpentry.org/license.html for more information.

How many molecules of different kinds can we

make using the atoms in our warehouse?

Sets and Dictionaries Nanotech Example

# Molecular formula file

helium : He 1

water : H 2 O 1

hydrogen : H 2

helium : He 1

water : H 2 O 1

hydrogen : H 2

# Atom inventory file

helium : He 1

water : H 2 O 1

hydrogen : H 2

# Atom inventory file

Now have all the tools we need

Natural to represent inventory as dictionary

Keys: atomic symbols

Values: number of atoms availableValues: number of atoms available

Represent individual molecules the same way

Store formulas as a dictionary of dictionaries

Keys: molecule names

Values: dictionaries of formulasValues: dictionaries of formulas

'water'

'ammonia'

Number of molecules that can be made is:

minavailable[atom]

required[atom]min required[atom]

atom ∈ formula

minavailable[atom]

atom ∈ formula

If atom not in available, its count is implicitly 0

minavailable[atom]

atom ∈ formula

Store results in yet another dictionary

minavailable[atom]

atom ∈ formula

minavailable[atom]

atom ∈ formula

Values: counts of how many can be made

'''Calculate how many molecules of each type can be made

with the atoms on hand.'''

importimportimportimport sys

ifififif __name__ == '__main__':ifififif __name__ == '__main__':

inventory = read_inventory(sys.argv[1])

formulas = read_formulas(sys.argv[2])

counts = calculate_counts(inventory, formulas)

show_counts(counts)

defdefdefdef read_inventory(filename):

'''Read inventory of available atoms.'''

result = {}

forforforfor line inininin read_lines(filename):

name, count = line.split(' ')name, count = line.split(' ')

result[name] = intintintint(count)

returnreturnreturnreturn result

defdefdefdef read_lines(filename):

'''Read lines from file, stripping out

blank lines and comments.'''

reader = openopenopenopen(filename, 'r')

lines = []lines = []

forforforfor line inininin reader:

line = line.split('#')[0].strip()

ifififif line:

lines.append(line)

reader.close()

returnreturnreturnreturn lines

defdefdefdef read_formulas(filename):

'''Read molecular formulas from file.'''

result = {}

name, atoms = line.split(':')

name = name.strip()

atoms = atoms.strip().split(' ')

formula = {}

forforforfor i inininin rangerangerangerange(0, lenlenlenlen(atoms), 2):

formula[atoms[i]] = int(atoms[i+1])

result[name] = formula

result = {}

Storing results

in dictionary

name = name.strip()

formula = {}

result = {}

For each

interesting

name = name.strip()

formula = {}

line in the

input file...

result = {}

forforforfor line inininin read_lines(filename):Separate the

name = name.strip()

formula = {}

Separate the

molecule name

and the formula

result = {}

forforforfor line inininin read_lines(filename):Separate the

name = name.strip()

formula = {}

Separate the

atoms and

their counts

result = {}

name = name.strip()

formula = {}

Loop over pairs

of atoms and

counts

result = {}

name = name.strip()

formula = {}

Store the count

as an integer

with the atomic

symbol as key

result = {}

name = name.strip()

formula = {}

And store the

molecule in

the main

dictionary

defdefdefdef calculate_counts(inventory, formulas):

'''Calculate how many of each molecule

can be made with inventory.'''

counts = {}

forforforfor name inininin formulas:forforforfor name inininin formulas:

counts[name] = dict_divide(inventory,

formulas[name])

returnreturnreturnreturn counts

counts = {}

formulas[name])

returnreturnreturnreturn countsSub-dictionary holding

atom counts for a

particular molecule

counts = {}

formulas[name])

Big functions: nothing is obviously wrong

counts = {}

formulas[name])

Big functions: nothing is obviously wrong

Small functions: obviously, nothing is wrong

defdefdefdef dict_divide(inventory, molecule):

'''Calculate how much of a single molecule

number = NoneNoneNoneNone

forforforfor atom inininin molecule:forforforfor atom inininin molecule:

required = molecule[atom]

available = inventory.get(atom, 0)

limit = available / required

ifififif (number isisisis None) orororor (limit < number):

number = limit

returnreturnreturnreturn number

forforforfor atom inininin molecule:

Identical format:

keys are atoms,forforforfor atom inininin molecule:

number = limit

keys are atoms,

values are counts

number = limit

Common pattern: None

returnreturnreturnreturn numbermeans "uninitialized",

so initialize the first

time through the loop

number = limit

Common pattern:

returnreturnreturnreturn numberstored value or default

number = limit

returnreturnreturnreturn numberCommon pattern:

find minimum of

calculated values

defdefdefdef show_counts(counts):

'''Show how many of each molecule can be made.'''

counts = invert_dict(counts)

forforforfor key inininin sortedsortedsortedsorted(counts.keys(), reverse=TrueTrueTrueTrue):

forforforfor name inininin sortedsortedsortedsorted(counts[key]):forforforfor name inininin sortedsortedsortedsorted(counts[key]):

printprintprintprint key, name

forforforfor name inininin sortedsortedsortedsorted(counts[key]):forforforfor name inininin sortedsortedsortedsorted(counts[key]):

Reverse to get

greatest first

defdefdefdef invert_dict(src):

'''Invert a dictionary, returning value->set{key}.'''

dst = {}

forforforfor key inininin src:

value = src[key]value = src[key]

ifififif value notnotnotnot inininin dst:

dst[value] = set()set()set()set()

dst[value].add(key)

returnreturnreturnreturn dst

defdefdefdef invert_dict(src):

'''Invert a dictionary, returning value->set{key}.'''

dst = {}

forforforfor key inininin src:

value = src[key]value = src[key]

ifififif value notnotnotnot inininin dst:

dst[value] = set()set()set()set()

dst[value].add(key)

returnreturnreturnreturn dst

Common pattern:

make sure there's a

collection, then add

ifififif key > 0:ifififif key > 0:

forforforfor name inininin sortedsortedsortedsorted(counts[key]):

Go back and only

show molecules that

can actually be made

# inventory-00.txt # formulas-01.txt

helium : He 1

No output, which is correct.

# inventory-01.txt

# formulas-01.txt

helium : He 1

1 helium

# inventory-02.txt

# formulas-01.txt

helium : He 1

1 helium

# inventory-02.txt

# formulas-02.txt

helium : He 1

water : H 2 O 1

1 helium

# inventory-02.txt

# formulas-03.txt

helium : He 1

water : H 2 O 1

hydrogen : H 2

2 hydrogen

1 helium

hydrogen : H 2

# inventory-03.txt

# formulas-03.txt

helium : He 1

water : H 2 O 1

hydrogen : H 2

2 hydrogen

2 water

1 helium

hydrogen : H 2

# inventory-03.txt

# formulas-03.txt

helium : He 1

water : H 2 O 1

hydrogen : H 2

2 hydrogen

2 water

1 helium

hydrogen : H 2

Looks good...

# inventory-03.txt

# formulas-03.txt

helium : He 1

water : H 2 O 1

hydrogen : H 2

2 hydrogen

2 water

1 helium

hydrogen : H 2

Looks good...

Code is much simpler than it would be using

lists of pairs

June 2010

created by

Greg Wilson

June 2010

This work is licensed under the Creative Commons Attribution License

See http://software-carpentry.org/license.html for more information.

nanotech example - v4.software-carpentry.org · sets and dictionaries nanotech example. how many...

Documents

paper presentation nanotech

nanotech painting

nanotech presentation final

nanomaterial and nanotech

commercialize nanotech

nanotech 2008 engl

nanotech · nanotech government policy, ion battery...

nanotech new

nanotech syllabus

sahabat nanotech

nanotech applications

nanotech 3567

cambridge nanotech overview

project - master nanotech

catalogo general nanotech

rise of nanotech

nanotech eagletry

dermal nanotech display

nanotech and biotech

bucky nanotech