Post by Chunxi Zhang
Chunxi's String&List
Write a function that reverses its string argument.
from test import testEqual
def reverse(astring):
return astring[::-1]
testEqual(reverse("happy"), "yppah")
testEqual(reverse("Python"), "nohtyP")
testEqual(reverse(""),"")
another input
from test import testEqual
def reverse(astring):
# your code here
a = list(astring)
a.reverse()
reversed = ''.join(a)
return reversed
testEqual(reverse("happy"), "yppah")
testEqual(reverse("Python"), "nohtyP")
testEqual(reverse(""),"")
same output
Pass
Pass
Pass
Write a function that mirrors its argument.
from test import testEqual
def reverse(mystr):
reversed = ''
for char in mystr:
reversed = char + reversed
return reversed
def mirror(mystr):
return mystr + reverse(mystr)
testEqual(mirror('good'),'gooddoog')
testEqual(mirror('Python'),'PythonnohtyP')
testEqual(mirror(''), '')
testEqual(mirror('a'),'aa')
output
Pass
Pass
Pass
Pass
Write a function that removes the first occurrence of a string from another string.
from test import testEqual
def remove(substr,theStr):
index = theStr.index(substr)
if index < 0：
return theStr
if index >= 0:
return the Str[:index]+theStr[index+len(substr):]
testEqual(remove('an', 'banana'),'bana')
testEqual(remove('cyc', 'bicycle'), 'bile')
testEqual(remove('iss', 'Mississippi'), 'Missippi')
testEqual(remove('egg', 'bicycle'), 'bicycle')
Output
Pass
Pass
Pass
Pass
Write a function that removes all occurrences of a string from another string.
from test import testEqual
def remove_all(substr,theStr):
new_string = theStr.replace(substr, "")
return new_string
testEqual(remove_all('an', 'banana'), 'ba')
testEqual(remove_all('cyc', 'bicycle'), 'bile')
testEqual(remove_all('iss', 'Mississippi'), 'Mippi')
testEqual(remove_all('eggs', 'bicycle'), 'bicycle')
Output
Pass
Pass
Pass
Pass
Write a function to count how many odd numbers are in a list.
import random
def countOdd(lst):
odd = 0
for e in lst:
if not e % 2 == 0:
odd = odd + 1
return odd
test = []
for i in range(611):
test.append(random.randint(0, 1000))
print(countOdd(test))
output
332
Sum up all the even numbers in a list.
import random
def sumEven(lst):
sum = 0
for e in lst:
if e % 2 == 0:
sum = sum + e
return sum
lst = []
for i in range(100):
lst.append(random.randrange(0, 100))
print(sumEven(lst))
output
2396
Sum up all the negative numbers in a list.
import random
def sumNegative(lst):
sum = 0
for e in lst:
if e < 0:
sum = sum + e
return sum
lst = []
for i in range(100):
lst.append(random.randrange(-1000, 1000))
print(sumNegative(lst))
output
-23563
Write a function replace(s, old, new) that replaces all occurences of old with new in a string s:
from test import testEqual
def replace(s, old, new):
lst = s.split(old)
return new.join(lst)
testEqual(replace('Mississippi', 'i', 'I'), 'MIssIssIppI')
s = 'I love spom! Spom is my favorite food. Spom, spom, spom, yum!'
testEqual(replace(s, 'om', 'am'),
'I love spam! Spam is my favorite food. Spam, spam, spam, yum!')
testEqual(replace(s, 'o', 'a'),
'I lave spam! Spam is my favarite faad. Spam, spam, spam, yum!')
output
Pass
Pass
Pass