Immutable
""" Strings are immutable, you can't change them
"""
str = "Hello World"
try:
str[0] = "J" # invalid statement
except TypeError as e:
print('TypeError:', e)
"""
TypeError: 'str' object does not support item assignment
"""
Slices
""" A string is a sequence of characters
We can slice a portion of it with [:]
"""
str = "banana"
# String slices
s1 = str[0:2] # first two chars
s2 = str[:2] # up to index 2
s3 = str[2:] # from index 2 to end
print(s1, s2, s3)
"""
ba ba nana
"""
Search Key
""" To search in a string, use a loop
Find key in a string
"""
def find_key(str, ch):
i = 0
while i < len(str):
if str[i] == ch:
return i
i = i + 1
return -1
key = find_key("Hello World", "o")
print(key)
"""
4
"""
in Operator
""" The `in` is a boolean operator
Returns True if the fist string appears as a substring in the second one
The repr() function returns a printable representation of the given object
"""
import os
file = os.path.dirname(__file__) + "/../data/words.txt"
rows = open(file)
def exists(word):
for char in word:
if char == "e":
return False
return True
W = [] # words
E = [] # word with no e
for row in rows:
word = row.strip()
W.append(word)
if (exists(word)):
E.append(word)
print("Words: " + repr(len(W)))
print("Words (with char e): " + repr(len(E)))
"""
Words: 113783
Words (with char e): 37621
"""
Last update: 266 days ago
