regular expressions

.gitignore

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+*.pyc
+*.o
+*.so
+*.gcno
+*.swp
+*.egg-info
+*.egg
+*~
+build
+dist
+lib/test
+doc/_build
+*.log
+*env
+*ENV

cmd_line_args_1_sysarg.py

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+# Getting command line arguments via sys.arg
+# sr 11/30/2013
+
+import sys
+
+def error(msg):
+    """Prints error message, sends it to stderr, and quites the program."""
+    sys.exit(msg)
+
+
+args = sys.argv[1:]     #  sys.argv[0] is the name of the python script itself
+
+try:
+    arg1 = int(args[0])
+    arg2 = args[1]
+    arg3 = args[2]
+    print("Everything okay!")
+
+except ValueError:
+    error("First argument must be integer type!")
+
+except IndexError:
+    error("Requires 3 arguments!")
+

reg_expr_1_basics.py

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+# Examples for using Python's Regular expression module "re"
+# sr 11/30/2013
+
+import re
+
+'''OVERVIEW
+     '|' means 'or'
+     '.' matches any single character 
+     '()' groups into substrings
+'''
+
+
+
+
+
+# read in data
+fileobj = '''abc mno
+def pqr
+ghi stu
+jkl vwx'''
+
+data = fileobj.strip().split('\n')
+
+
+# A >> if 's' in line
+print (50*'-' + '\nA\n' + 50*'-')
+for line in data:
+    if re.search('abc', line):
+        print(">>", line)
+    else:
+        print("  ", line)
+
+'''
+--------------------------------------------------
+A
+--------------------------------------------------
+>> abc mno
+   def pqr
+   ghi stu
+   jkl vwx'''
+
+
+
+# B >> if 's' in line or 'r' in line
+print (50*'-' + '\nB\n' + 50*'-')
+for line in data:
+    if re.search('abc|efg', line):
+        print(">>", line)
+    else:
+        print("  ", line)
+
+'''
+--------------------------------------------------
+B
+--------------------------------------------------
+>> abc mno
+   def pqr
+   ghi stu
+   jkl vwx
+---------------'''
+
+
+# C >> 
+# use () to remember which object was found and return a match object
+print (50*'-' + '\nC\n' + 50*'-')
+for line in data:
+    match = re.search('(abc|efg)', line)    # note the parantheses
+    if match: 
+        print(match.group(1))               # prints 'abc' if found, else None
+        # match.group(0) is the whole pattern that matched
+
+'''
+--------------------------------------------------
+C
+--------------------------------------------------
+abc'''
+
+
+
+# read in data
+fileobj = '''2013-01-01
+2012-02-02
+ghi stu
+2012-03-03'''
+
+data = fileobj.strip().split('\n')
+
+
+# D >> use '.' to match 'any character'
+print (50*'-' + '\nD\n' + 50*'-')
+for line in data:
+    match = re.search('(2012)-(..)-(..)', line)    # note the parantheses
+    if match: 
+        print(match.group(1), match.group(2), match.group(3))             
+
+'''
+--------------------------------------------------
+D
+--------------------------------------------------
+2012 02 02
+2012 03 03'''

reg_expr_2_operators.py

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+# Examples for using Python's Regular expression module "re"
+# sr 11/30/2013
+
+import re
+
+'''OVERVIEW
+     '*' matches all characters that follow (0 or more)
+     '+' matches all characters that follow (1 or more)
+     '?' makes the previous character optional
+     '{4}' previous character must match exactly 4 times
+     '{2-4}' previous character must match exactly 2-4 times  
+'''
+
+data = '''2013-01-01
+2012-02-02
+aaaa-02-02
+aa-02-02
+-04-04
+2000 02-02
+ghi stu
+2012-03-03'''.strip().split('\n')
+
+
+# A >> '*' matches all characters that follow (0 or more)
+print (50*'-' + '\nA\n' + 50*'-')
+
+for line in data:
+    match = re.search('(.*)-(..)-(..)', line)    # note the parantheses
+    if match: 
+        print(match.group(1), match.group(2), match.group(3))  
+
+'''
+--------------------------------------------------
+A
+--------------------------------------------------
+2013 01 01
+2012 02 02
+aaaa 02 02
+aa 02 02
+ 04 04
+2012 03 03
+'''
+
+
+# B >> '+' matches all characters that follow (1 or more)
+print (50*'-' + '\nB\n' + 50*'-')
+
+for line in data:
+    match = re.search('(.+)-(..)-(..)', line)    # note the parantheses
+    if match: 
+        print(match.group(1), match.group(2), match.group(3))  
+
+'''
+--------------------------------------------------
+B
+--------------------------------------------------
+2013 01 01
+2012 02 02
+aaaa 02 02
+aa 02 02
+2012 03 03
+'''
+
+
+# C >> '?' makes the previous character optional
+print (50*'-' + '\nC\n' + 50*'-')
+
+for line in data:
+    match = re.search('(.+)-?(..)-(..)', line)    # note the parantheses
+    if match: 
+        print(match.group(1), match.group(2), match.group(3)) 
+
+'''
+--------------------------------------------------
+C
+--------------------------------------------------
+2013- 01 01
+2012- 02 02
+aaaa- 02 02
+aa- 02 02
+- 04 04
+2000  02 02
+2012- 03 03
+'''
+
+# D >> '{4}' previous character must match exactly 4 times 
+print (50*'-' + '\nD\n' + 50*'-')
+
+for line in data:
+    match = re.search('(a{4})-(..)-(..)', line)    # note the parantheses
+    if match: 
+        print(match.group(1), match.group(2), match.group(3)) 
+
+'''
+--------------------------------------------------
+D
+--------------------------------------------------
+aaaa 02 02
+'''
+
+# E >>'{2-4}' previous character must match exactly 2-4 times
+print (50*'-' + '\nE\n' + 50*'-')
+
+for line in data:
+    match = re.search('(a{2,4})-(..)-(..)', line)    # note the parantheses
+    if match: 
+        print(match.group(1), match.group(2), match.group(3)) 
+
+'''
+--------------------------------------------------
+E
+--------------------------------------------------
+aaaa 02 02
+aa 02 02
+'''