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--- public:t-malv-15-3:3 [2015/09/02 23:38] – [4. rot13.py: Read and Write file] orvark
+++ public:t-malv-15-3:3 [2024/04/29 13:33] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 ====== Lab 3 ======
-**Try to complete as many problems as you can. Hand in your code files with what you have finished in MySchool before midnight today (3 September). **
+**Try to complete as many of the problems as you can. Hand in your code files with what you have done in MySchool before midnight today (3 September). **
-The first and the last problems should be in a file named ''lab3.py'', the others in ''myscript.py'', ''tokenize.py'' and ''rot13.py''.
+The first and the last problems should be in a file named ''lab3.py'', the others in ''myscript.py'', ''mytokenize.py'' and ''rot13.py''.
 If you can't manage to complete a particular problem please hand in your incomplete code -- comment it out if it produces an error.
@@ Line 31: / Line 31: @@
 <code>
 $ python myscript.py One TWO three
-['lab3-1.py', 'One', 'TWO', 'three']
+['myscript.py', 'One', 'TWO', 'three']
 </code>
@@ Line 51: / Line 51: @@
 Second parameter: file2.txt
 </code>
+**NOTE: The python installer for Windows does not seem to add python to the path by default. If you can't invoke python in the Command Prompt (cmd) the simplest solution might be to install python again (choose "Change Python") and then make sure "Add python.exe to Path" is selected (last option undir "Customize Python").**
+{{:public:t-malv-15-3:python-path-install.png?direct&200|}}
 ([[https://docs.python.org/3.3/using/cmdline.html#using-on-cmdline|Information on executing python scripts in Windows]])
-===== 3. tokenize.py: Read file =====
+===== 3. mytokenize.py: Read file =====
-**Create a script name ''tokenize.py'' that reads a file contents, tokenizes them, removes stopwords and print out the remaining tokens, one per line.**
+**Create a script name ''mytokenize.py'' that reads a file contents, tokenizes them, removes stopwords and print out the remaining tokens, one per line.**
 <code python>
@@ Line 65: / Line 69: @@
 #Get file name from argv (see problem 3).
 #Open file for reading.
-#Read contents into string.
+#Read contents into a string.
 #Tokenize the string.
 #Remove stopwords (words in stopwords.words('english')).
@@ Line 71: / Line 75: @@
 </code>
-You should be able to invoke the script using ''python tokenize.py test.txt''.
+You should be able to invoke the script using ''python mytokenize.py test.txt''.
@@ Line 85: / Line 89: @@
 #Open file1 for reading.
 #Open file2 for writing.
-#  Read one line from file1.
+#  Loop; read one line from file1.
      line = encode(line, 'rot_13')
 #    Write the line to file2.
@@ Line 105: / Line 109: @@
 ===== 5. List comprehension ====
-Rewrite the following loop as a **list comprehension**:
+**Rewrite the following loop as a "list comprehension"**:
 <code python>
@@ Line 124: / Line 128: @@
 **If you feel this problem is easy you should also try your hand at problems 31 and 41.**
+===== Possible Solutions =====
+<code python>
+#1
+>>> monty[::-1] == 'nohtyP ytnoM'
+True
+#2
+from sys import argv
+print('Number of parameters: ', len(argv)-1)
+print('Script name: ', argv[0])
+print('First parameter: ', argv[1])
+print('Second parameter: ', argv[2])
+#3
+from sys import argv
+from nltk import word_tokenize
+from nltk.corpus import stopwords
+with open(argv[1]) as infile:
+    for w in word_tokenize(infile.read()):
+        if w.lower() not in stopwords.words('english'):
+            print(w)
+#Since files are context managers, they can be used in a with-statement.
+#The file will close when the code block is finished, even if an exception occurs
+#4
+from sys import argv
+from codecs import encode
+with open(argv[1]) as infile, open(argv[2], 'w') as outfile:
+    for line in infile:
+        outfile.write(encode(line, 'rot_13'))
+#5
+[(w, len(w)) for w in sent]
+</code>