basic_python

First

For Python 2

print 'hello'

For Python 3

print('hello')

Comment

# print 'hello'

Data type

Python is dynamic typed.

x = 54
y = 5.4
s = 'hello'
b = True

print 'x: {}'.format(x)

print '{s} {x}'.format(s=s, x=x)

print '{sakura} {xmen}'.format(sakura=s, xmen=x)

List

a = [1, 234, 45, 45]
b = ['hello', 'python']

a[-1]

a[0:2]

s[0:4]

a[1] = a[1] - 1

b.append('world')

len(a)

a.count(456)

234 in a

Dictionary

d = {'key': 'Value', 'last': 'Suzuki'}

d['last']

d['first'] = 'Alto'

Tuple

t = (100, 200)

Control

if x == 54:
    print 'yes'
elif x == 5.4:
    print 'no'
else:
    print 'NO'

while x == 54:
    print 'yes'

for item in a:
    print item

Exception

z += 1

try:
    z += 1
except:
    z = 0
    z += 1

Exercises

# Replace space in string with underscore
s = 'sublime text'
w = s.split()
s = '_'.join(w)
print s

# Split string by symbol
s = '   this ;is;  so;  fun  '
w = s.split(';')
# ... and also cleanup the whitespaces
w = []
for r in s.split(';'):
    w.append(r.strip())

w = [r.strip() for r in s.split(';')]

# Make a copy of the list without duplicated numbers
a = [1, 2, 3, 3, 5, 5, 6]
b = []
...

# Count number of duplicate of each unique number in the list
a = [10, 10, 20, 20, 10, 20, 10, 30, 30, 40]

# Expected result: count = {10: 4, 20: 3, 30: 2, 40: 1}

Read and write to file

s = 'label_a,label_b,label_c'

with open('test.txt', 'w') as f:
    f.write(s + '\n')

with open('text.txt', 'r') as f:
    for line in f:
        print line