Python Training at VMWare - Day 2¶
Feb 26-28, 2018 Vikrant Patil
These notes are available online at http://notes.pipal.in/2018/vmware-feb-python
© Pipal Academy LLP
In [3]:
def fibseries(n):
"""
generates list of fibonacci numbers less than n
"""
prev, current = 1,1
series = []
while prev < n:
series.append(prev)
prev, current = current, current+prev
return series
In [4]:
fibseries(100)
Out[4]:
In [6]:
fibs = fibseries(100)
fibs
Out[6]:
In [7]:
sqrfib = []
for f in fibs:
print(f,end=",")
In [8]:
sqrfib = []
for f in fibs:
sqr = f*f
sqrfib.append(sqr)
In [9]:
sqrfib
Out[9]:
In [10]:
names = ["Alice","Elsa","Harry","Alex"]
In [11]:
for name in names:
print(name.upper())
In [12]:
person = {"name":"Alice","email":"alice@example.com","website":"http://alice.example.com"}
In [13]:
for key in person:
print(key)
In [14]:
for key in person:
print(person[key])
In [15]:
for key in person:
print(key, person[key])
In [16]:
for char in "just for checking for loops over string":
print(char, end=",")
In [17]:
for color in (256,256,0):
print(color)
In [18]:
for i in range(10):
print(i, end=",")
In [19]:
for p in [2,3,5,7,11,13]:
print(p, end=",")
In [22]:
for item in set("just for checking for loops over sets"):
print(item, end=",")
problems
- Write a python script ls.py which mimics unix command ls approximately. it prints every filename from given directory on new line.
python ls.py . day1.ipynb day1.html module.py module1.py - Write a function
productwhich finds proudct of all items from given collection of numbers. - Write a function
factorialwhich computes factorial of given number
In [23]:
list(range(5))
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In [24]:
list(range(2,6))
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In [26]:
n= 5
list(range(1,n+1))
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In [27]:
%%file ls.py
import sys
import os
def ls(dirpath):
files = os.listdir(dirpath)
for file in files:
print(file)
if __name__=="__main__":
if len(sys.argv)==1:
ls(os.getcwd())
else:
ls(sys.argv[1])
In [28]:
!python ls.py
In [29]:
!python ls.py /tmp
In [30]:
def product(numbers):
p = 1
for n in numbers:
p *= n
return p
def factorial(n):
return product(range(1,n+1))
In [32]:
product([3,4,5,6])
Out[32]:
In [33]:
factorial(5)
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In [36]:
def print_primes(n):
"""
print all primes less than or equal to n
"""
for i in range(1,n+1):
for j in range(2,i):
if i%j==0:
break
else:
print(i,end=",")
In [37]:
print_primes(20)
In [38]:
def squares(numbers):
sqrs = []
for n in numbers:
sqrs.append(n*n)
return sqrs
def evens(numbers):
def even(x):
return x%2==0
e = []
for n in numbers:
if even(n):
e.append(n)
return e
In [39]:
squares([2,3,4,5])
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In [40]:
evens(range(10))
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In [41]:
fibs
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In [43]:
fibs[:2] # take first two
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In [44]:
fibs[2:] # drop first two
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In [45]:
fibs[2:5] # start at 2nd index end at 5th index(excluding)
Out[45]:
In [46]:
fibs[1:6:2] ## start at 1st index end at 6th index(excluding) at step of 2
Out[46]:
In [47]:
fibs[:]
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In [50]:
fibs[:-1] #drop last one
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In [51]:
fibs[:-2] # drop last two
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In [52]:
fibs[::-1]
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In [53]:
def is_palindrom(word):
return word == word[::-1]
In [54]:
is_palindrom("madam")
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In [55]:
is_palindrom("hello")
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problems
- Write a function
split_atwhich splits given list in two parts breaking original list at given index
In [56]:
def split_at(items, n):
return items[:n],items[n:]
In [58]:
split_at(list(range(10)), 3)
Out[58]:
problem
- Write a function
find_extensionto find extension of given file.>>> find_extension("xyz.tar.gz") "gz"
In [59]:
s = "do geese see god"
In [60]:
s[100]
In [61]:
s[:100]
Out[61]:
list comprehensions¶
In [63]:
[i*i for i in range(7)]
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In [65]:
[i*i*i for i in range(7)]
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In [66]:
[w.upper() for w in names]
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In [68]:
[i for i in range(7)]
Out[68]:
In [69]:
[i for i in range(7) if i%2==0]
Out[69]:
In [70]:
[i for i in range(1,6)]
Out[70]:
In [72]:
t = [[i*j for i in range(1,6)] for j in range(1,11)]
In [73]:
t
Out[73]:
In [74]:
t[0]
Out[74]:
In [75]:
t[-1]
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In [77]:
t[0][-1] # last item from 0th row
Out[77]:
problems
- Write a function to generate list of python files from given directory
>>> listpy(os.getcwd()) ['module.py','module1.py','add.py'] - Write a function
factorswhich finds all factors of given number.>>> factors(5) [1,5] >>> factors(6) [1,2,3,6] - make use of fact that prime number has only two factors 1 and self to write a function
is_primewhich determines if given number is prime or not. - Write a list comprehension to generates primes using above function.
In [78]:
def listpy(path):
return [f for f in os.listdir(path) if f.endswith(".py")]
In [80]:
import os
listpy(os.getcwd())
Out[80]:
In [81]:
def factors(n):
return [i for i in range(1,n+1) if n%i==0]
In [82]:
factors(5)
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In [83]:
def is_prime(n):
return factors(n)==[1,n]
In [84]:
def primes(n):
return [p for p in range(1,n+1) if is_prime(p)]
In [85]:
primes(20)
Out[85]:
problem
- Generate a unit matrix of dimension 5x5 using list comprehensions.
- sum all multiples of 7 or 11 below 1000
In [86]:
[[i*j for i in range(5)] for j in range(5)]
Out[86]:
In [87]:
[[i==j for i in range(5)] for j in range(5)]
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In [88]:
[[int(i==j) for i in range(5)] for j in range(5)]
Out[88]:
In [89]:
[[1 if i==j else 0 for i in range(5)] for j in range(5)]
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In [90]:
[[{True:1,False:0}[i==j] for i in range(5)] for j in range(5)]
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In [91]:
t
Out[91]:
In [92]:
t[0]
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In [93]:
t[0][0]
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In [95]:
t[0][:]
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In [96]:
def column(data, n):
rows = len(data)
return [data[i][n] for i in range(rows)]
In [97]:
column(t, 0)
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In [98]:
t
Out[98]:
In [99]:
column(t, 1)
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In [102]:
def transpose(data):
cols = len(data[0])
return [column(data, i) for i in range(cols)]
In [101]:
transpose(t)
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In [103]:
def reverse(item):
return item[::-1]
In [104]:
def rotate90clockwise(data):
cols = len(data[0])
return [reverse(column(data, i)) for i in range(cols)]
In [105]:
rotate90clockwise(t)
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Iteration patterns¶
In [106]:
for i in primes(20):
print(i, end=",")
In [113]:
for i in reversed(primes(20)):
print(i, end=",")
In [114]:
reversedprimes = reversed(primes(20))
In [115]:
for p in reversedprimes:
print(p, end=",")
In [116]:
for p in reversedprimes:
print(p, end=",")
In [117]:
multiline = """
one
two
three
four
five
"""
In [118]:
lines = multiline.strip().split()
In [119]:
lines
Out[119]:
In [122]:
for index,line in enumerate(lines):
print(index, line)
In [126]:
for ind,value in enumerate(lines):
print(ind, value)
In [123]:
names = ["Elsa","Elisa","Alex","David"]
surnames = ["Frozen","Hacker","Lion","Beazley"]
In [124]:
for n, s in zip(names, surnames):
print(n,s)
In [128]:
lines1 = [[l,l,l] for l in lines]
In [129]:
lines1
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In [130]:
list(enumerate(lines1))
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In [131]:
ids = range(len(names))
In [132]:
for id_,n,s in zip(ids,names, surnames):
print(id_, n, s)
In [133]:
for id_,n in zip(ids,names, surnames):
print(id_, n, s)
In [134]:
for id_,n,s,a in zip(ids,names, surnames):
print(id_, n, s)
problem
- Write a function vector_add which adds elements from two lists item by item.
In [135]:
def vector_add(v1, v2):
return sum(x+y for x,y in zip(v1, v2))
In [136]:
vector_add(range(10),range(10))
Out[136]:
problem
- Implement quicksort which sorts list of numbers based on strategy of pivoting.
In [137]:
[1,23] + [23,45]
Out[137]:
In [138]:
[1,2,3] + [3] + [4,5,6]
Out[138]:
In [139]:
[1,2,3] + [3]
Out[139]:
In [140]:
def quick(items):
if items==[]:
return []
p = items[0]
less = [i for i in items[1:] if i<=p]
more = [i for i in items[1:] if i>p]
return quick(less) + [p] + quick(more)
In [141]:
quick([23,2,12,56,1,2,3,9,1,8,2])
Out[141]:
String formating¶
In [142]:
for i in range(1,11):
print(i, i*i, i*i*i)
In [143]:
for i in range(1,11):
print(str(i).rjust(2), str(i*i).rjust(3), str(i*i*i).rjust(4))
In [144]:
"wizard of {} is {}".format("oz", "python")
Out[144]:
In [145]:
"wizard of {1} is {0}".format("python","oz")
Out[145]:
In [146]:
"wizard of {wiz} is in {place}".format(wiz="python", place="oz")
Out[146]:
In [147]:
for i in range(1,11):
print("{num:2d} {sqr:3d} {cube:4d}".format(num=i,sqr=i*i,cube=i**3))
problem
- Write a function
pascalwhich generates pascal triangle as list of list as shon below. the triangle shown below should be generated as a list [[1],[1,1],[1,2,1]]1 1 1 1 2 1 - Write a function to pretty print pascal triangle.
In [151]:
def pascal(base):
t = [[1]]
for i in range(base-1):
prevbase = t[-1]
pre = [0] + prevbase
post = prevbase + [0]
newbase = [x+y for x,y in zip(pre, post)]
t.append(newbase)
return t
In [150]:
def pascal_(base):
t = [[1]]
for i in range(base-1):
prevbase = t[-1]
baseln = len(prevbase)
newbase = [1] + [prevbase[i]+prevbase[i+1] for i in range(baseln-1)] + [1]
t.append(newbase)
return t
In [152]:
pascal(5)
Out[152]:
In [153]:
pascal_(5)
Out[153]:
In [168]:
def print_pascal(t):
def formatrow(row):
s = ""
for item in row:
s = s + "{item:{maxdigits}d}".format(item=item, maxdigits=maxdigits+1)
return s
maxdigits = len(str(max(t[-1])))
basesize = len(t[-1])
maxwidth = basesize*maxdigits + basesize -1
for row in t:
strrow = formatrow(row)
print(strrow.center(maxwidth))
In [169]:
print_pascal(pascal(16))
In [170]:
%matplotlib inline
In [ ]:
In [171]:
import matplotlib.pyplot as plt
def imshow(img):
plt.imshow(img,cmap=plt.cm.gray)
plt.show()
In [172]:
imshow(t)
In [173]:
imshow(transpose(t))
In [174]:
imshow(rotate90clockwise(t))
Testing¶
In [178]:
%%file functions.py
def square(x):
"""
>>> square(-1)
1
>>> square(1)
1
"""
return x*x
def sumofsquares(x,y):
"""
>>> sumofsquares(2,3)
13
>>> sumofsquares(-1,-1)
2
"""
return square(x) + square(y)
def add(x,y):
"""
>>> add(1,2)
1
"""
return x+y
In [179]:
!python -m doctest -v functions.py
In [189]:
%%file functions.py
def square(x):
"""
>>> square(-1)
1
>>> square(1)
1
"""
return x*x
def sumofsquares(x,y):
"""
>>> sumofsquares(2,3)
13
>>> sumofsquares(-1,-1)
2
"""
return square(x) + square(y)
def add(x,y):
"""
>>> add(1,2)
1
"""
return x+y
def test_square():
assert square(-1) == 1
assert square(2)== 4
assert square(4) == 15
def test_sumofsquares():
assert sumofsquares(2,3)==13
assert sumofsquares(-1,-1)==2
def hello_test():
assert 1 == 2
def test123():
assert 2==3
def testsum():
print(sum(range(10)))
In [190]:
!py.test -v functions.py
To install pytest use following command
pip3 install pytestWorking with files¶
In [191]:
import this
In [192]:
%%file data.txt
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!
In [193]:
f = open("data.txt")
In [194]:
f.read()
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In [195]:
f.read()
Out[195]:
In [196]:
f.close()
In [197]:
f = open("data.txt")
In [198]:
f.readline()
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In [199]:
f.readline()
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In [200]:
f.readline()
Out[200]:
In [202]:
f = open("data.txt")
line = f.readline()
while line:
print(line, end="")
line = f.readline()
In [203]:
f = open("data.txt")
In [204]:
lines = f.readlines()
In [205]:
lines
Out[205]:
In [206]:
for line in open("data.txt"):
print(line, end="")
In [207]:
list(open("data.txt"))
Out[207]:
In [ ]: